presentation layer system architecture

Layered Architecture

Last updated: November 11, 2021

• Software Architecture

1. Introduction

In this article, we’re going to look at the layered architecture in software development. We’ll give an overview of what it is, its components, and outline its characteristics. Next, we’ll also describe the benefits and drawbacks, and give examples of situations where they are appropriate for use.

Before we begin, let’s first define software architecture.

2. Definitions

Software architecture refers to the basic structure of any software system and incorporates any aspect that makes a system function and behaves as it should . Although the term architecture usually refers to physical designs, in software systems, it encompasses the design of components, relationships between components, user interactions, as as well as the user’s needs of a system.

There are several different software architectures that exist such as microkernels, microservices , and client-servers just to name a few. Each of these is structured differently and is used in a different context. However, we’ll only look at layered architectures in this article.

3. What Is a Layered Architecture?

Layered architectures are said to be the most common and widely used architectural framework in software development. It is also known as an n-tier architecture and describes an architectural pattern composed of several separate horizontal layers that function together as a single unit of software . A layer is a logical separation of components or code:

In these frameworks, components that are related or that are similar are usually placed on the same layers . However, each layer is different and contributes to a different part of the overall system.

3.1. Characteristics

A major characteristic of this framework is that layers are only connected to the layers directly below them. In the illustration given previously, layer 1 only connects to layer 2, layer 2 connects to layer 3, and layer 1 is connected to layer 3 only through layer 2.

Another characteristic is the concept of layers of isolation . This means that layers can be modified and the change won’t affect other layers . In short, changes are isolated to the specific layer that is altered.

Separation of concerns is another notable feature that speaks to how the modules on a single layer together perform a single function .

4. Components of a Layered Architecture

Now, the number of layers in a layered architecture is not set to a specific number and is usually dependent on the developer or software architect. It is important to note that this framework will usually always have a user interaction layer, a layer for processing, and a layer that deals with data processing. These are described further as:

• Presentation Layer – responsible for user interactions with the software system
• Application/Business Layer – handles aspects related to accomplishing functional requirements
• Domain Layer – responsible for algorithms, and programming components
• Infrastructure/Persistence/Database Layer – responsible for handling data, databases

Additionally, in some applications, some layers are combined. For example, it is common to find the business layer and persistence layer combined into a single layer. This just means that the functions and responsibilities of these two layers have been grouped to occur at a single layer.

5. Advantages and Disadvantages

The following are the benefits and drawbacks that exist with this software pattern:

• The framework is simple and easy to learn and implement.
• There is reduced dependency because the function of each layer is separate from the other layers.
• Testing is easier because of the separated components, each component can be tested individually.
• Cost overheads are fairly low.

Disadvantages

• Scalability is difficult because the structure of the framework does not allow for growth.
• They can be difficult to maintain. A change in a single layer can affect the entire system because it operates as a single unit.
• There is interdependence between layers since a layer depends on the layer above it to receive data.
• Parallel processing is not possible.

6. When to Use Layered Architectures

When developing simple, small applications, it is advisable to implement a layered architecture because it’s the most simple framework. However, some developers are of the opinion that because they can be difficult to maintain, it is better to apply them to larger projects.

In spite of this, the framework can be used for applications that need to be built quickly because it’s easy to learn and implement. It is also good in cases where the developers do not have a lot of knowledge of software architectures or when they are undecided on which one to use.

Some real-life applications of this architecture are in web applications and the OSI model . The J2EE programming model also implements the layered architecture.

7. Conclusions

In this article, we’ve defined layered architectures. We’ve also discussed their characteristics and the basic components that exist. We’ve looked at the benefits and drawbacks and have also detailed scenarios where it is appropriate to use them.

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Chapter 1. Layered Architecture

The most common architecture pattern is the layered architecture pattern, otherwise known as the n-tier architecture pattern. This pattern is the de facto standard for most Java EE applications and therefore is widely known by most architects, designers, and developers. The layered architecture pattern closely matches the traditional IT communication and organizational structures found in most companies, making it a natural choice for most business application development efforts. 

Pattern Description

Components within the layered architecture pattern are organized into horizontal layers, each layer performing a specific role within the application (e.g., presentation logic or business logic). Although the layered architecture pattern does not specify the number and types of layers that must exist in the pattern, most layered architectures consist of four standard layers: presentation, business, persistence, and database ( Figure 1-1 ). In some cases, the business layer and persistence layer are combined into a single business layer, particularly when the persistence logic (e.g., SQL or HSQL) is embedded within the business layer components. Thus, smaller applications may have only three layers, whereas larger and more complex business applications may contain five or more layers. 

Each layer of the layered architecture pattern has a specific role and responsibility within the application. For example, a presentation layer would be responsible for handling all user interface and browser communication logic, whereas a business layer would be responsible for executing specific business rules associated with the request. Each layer in the architecture forms an abstraction around the work that needs to be done to satisfy a particular business request. For example, the presentation layer doesn’t need to know or worry about how to get customer data; it only needs to display that information on a screen in particular format. Similarly, the business layer doesn’t need to be concerned about how to format customer data for display on a screen or even where the customer data is coming from; it only needs to get the data from the persistence layer, perform business logic against the data (e.g., calculate values or aggregate data), and pass that information up to the presentation layer.  

Figure 1-1. Layered architecture pattern

One of the powerful features of the layered architecture pattern is the separation of concerns among components. Components within a specific layer deal only with logic that pertains to that layer. For example, components in the presentation layer deal only with presentation logic, whereas components residing in the business layer deal only with business logic. This type of component classification makes it easy to build effective roles and responsibility models into your architecture, and also makes it easy to develop, test, govern, and maintain applications using this architecture pattern due to well-defined component interfaces and limited component scope.

Key Concepts

Notice in Figure 1-2 that each of the layers in the architecture is marked as being  closed . This is a very important concept in the layered architecture pattern. A closed layer means that as a request moves from layer to layer, it must go through the layer right below it to get to the next layer below that one. For example, a request originating from the presentation layer must first go through the business layer and then to the persistence layer before finally hitting the database layer. 

Figure 1-2. Closed layers and request access

So why not allow the presentation layer direct access to either the persistence layer or database layer? After all, direct database access from the presentation layer is much faster than going through a bunch of unnecessary layers just to retrieve or save database information. The answer to this question lies in a key concept known as  layers of isolation . 

The layers of isolation concept means that changes made in one layer of the architecture generally don’t impact or affect components in other layers: the change is isolated to the components within that layer, and possibly another associated layer (such as a persistence layer containing SQL). If you allow the presentation layer direct access to the persistence layer, then changes made to SQL within the persistence layer would impact both the business layer and the presentation layer, thereby producing a very tightly coupled application with lots of interdependencies between components. This type of architecture then becomes very hard and expensive to change.  

The layers of isolation concept also means that each layer is independent of the other layers, thereby having little or no knowledge of the inner workings of other layers in the architecture. To understand the power and importance of this concept, consider a large refactoring effort to convert the presentation framework from JSP (Java Server Pages) to JSF (Java Server Faces). Assuming that the contracts (e.g., model) used between the presentation layer and the business layer remain the same, the business layer is not affected by the refactoring and remains completely independent of the type of user-interface framework used by the presentation layer.  

While closed layers facilitate layers of isolation and therefore help isolate change within the architecture, there are times when it makes sense for certain layers to be open. For example, suppose you want to add a shared-services layer to an architecture containing common service components accessed by components within the business layer (e.g., data and string utility classes or auditing and logging classes). Creating a services layer is usually a good idea in this case because architecturally it restricts access to the shared services to the business layer (and not the presentation layer). Without a separate layer, there is nothing architecturally that restricts the presentation layer from accessing these common services, making it difficult to govern this access restriction.  

In this example, the new services layer would likely reside  below  the business layer to indicate that components in this services layer are not accessible from the presentation layer. However, this presents a problem in that the business layer is now required to go through the services layer to get to the persistence layer, which makes no sense at all. This is an age-old problem with the layered architecture, and is solved by creating open layers within the architecture.  

As illustrated in Figure 1-3 , the services layer in this case is marked as open,  meaning requests are allowed to bypass this open layer and go directly to the layer below it. In the following example, since the services layer is open, the business layer is now allowed to bypass it and go directly to the persistence layer, which makes perfect sense.  

Figure 1-3. Open layers and request flow

Leveraging the concept of open and closed layers helps define the relationship between architecture layers and request flows and also provides designers and developers with the necessary information to understand the various layer access restrictions within the architecture. Failure to document or properly communicate which layers in the architecture are open and closed (and why) usually results in tightly coupled and brittle architectures that are very difficult to test, maintain, and deploy.

Pattern Example

To illustrate how the layered architecture works, consider a request from a business user to retrieve customer information for a particular individual as illustrated in Figure 1-4 . The black arrows show the request flowing down to the database to retrieve the customer data, and the red arrows show the response flowing back up to the screen to display the data. In this example, the customer information consists of both customer data and order data (orders placed by the customer).  

The customer screen is responsible for accepting the request and displaying the customer information. It does not know where the data is, how it is retrieved, or how many database tables must be queries to get the data. Once the customer screen receives a request to get customer information for a particular individual, it then forwards that request onto the customer delegate module. This module is responsible for knowing which modules in the business layer can process that request and also how to get to that module and what data it needs (the contract). The customer object in the business layer is responsible for aggregating all of the information needed by the business request (in this case to get customer information). This module calls out to the  customer dao  (data access object) module in the persistence layer to get customer data, and also the order dao module to get order information. These modules in turn execute SQL statements to retrieve the corresponding data and pass it back up to the customer object in the business layer. Once the customer object receives the data, it aggregates the data and passes that information back up to the customer delegate, which then passes that data to the customer screen to be presented to the user.      

Figure 1-4. Layered architecture example

From a technology perspective, there are literally dozens of ways these modules can be implemented. For example, in the Java platform, the customer screen can be a (JSF) Java Server Faces screen coupled with the customer delegate as the managed bean component. The customer object in the business layer can be a local Spring bean or a remote EJB3 bean. The data access objects illustrated in the previous example can be implemented as simple POJO’s (Plain Old Java Objects), MyBatis XML Mapper files, or even objects encapsulating raw JDBC calls or Hibernate queries. From a Microsoft platform perspective, the customer screen can be an ASP (active server pages) module using the .NET framework to access C# modules in the business layer, with the customer and order data access modules implemented as ADO (ActiveX Data Objects). 

Considerations

The layered architecture pattern is a solid general-purpose pattern, making it a good starting point for most applications, particularly when you are not sure what architecture pattern is best suited for your application. However, there are a couple of things to consider from an architecture standpoint when choosing this pattern.

The first thing to watch out for is what is known as the architecture sinkhole anti-pattern . This anti-pattern describes the situation where requests flow through multiple layers of the architecture as simple pass-through processing with little or no logic performed within each layer. For example, assume the presentation layer responds to a request from the user to retrieve customer data. The presentation layer passes the request to the business layer, which simply passes the request to the persistence layer, which then makes a simple SQL call to the database layer to retrieve the customer data. The data is then passed all the way back up the stack with no additional processing or logic to aggregate, calculate, or transform the data. 

Every layered architecture will have at least some scenarios that fall into the architecture sinkhole anti-pattern. The key, however, is to analyze the percentage of requests that fall into this category. The 80-20 rule is usually a good practice to follow to determine whether or not you are experiencing the architecture sinkhole anti-pattern. It is typical to have around 20 percent of the requests as simple pass-through processing and 80 percent of the requests having some business logic associated with the request. However, if you find that this ratio is reversed and a majority of your requests are simple pass-through processing, you might want to consider making some of the architecture layers open, keeping in mind that it will be more difficult to control change due to the lack of layer isolation. 

Another consideration with the layered architecture pattern is that it tends to lend itself toward monolithic applications, even if you split the presentation layer and business layers into separate deployable units. While this may not be a concern for some applications, it does pose some potential issues in terms of deployment, general robustness and reliability, performance, and scalability.   

Pattern Analysis

The following table contains a rating and analysis of the common architecture characteristics for the layered architecture pattern. The rating for each characteristic is based on the natural tendency for that characteristic as a capability based on a typical implementation of the pattern, as well as what the pattern is generally known for. For a side-by-side comparison of how this pattern relates to other patterns in this report, please refer to  Appendix A  at the end of this report.

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Prerequisite : OSI Model

Introduction : Presentation Layer is the 6th layer in the Open System Interconnection (OSI) model. This layer is also known as Translation layer, as this layer serves as a data translator for the network. The data which this layer receives from the Application Layer is extracted and manipulated here as per the required format to transmit over the network. The main responsibility of this layer is to provide or define the data format and encryption. The presentation layer is also called as Syntax layer since it is responsible for maintaining the proper syntax of the data which it either receives or transmits to other layer(s).

Functions of Presentation Layer :

The presentation layer, being the 6th layer in the OSI model, performs several types of functions, which are described below-

• Presentation layer format and encrypts data to be sent across the network.
• This layer takes care that the data is sent in such a way that the receiver will understand the information (data) and will be able to use the data efficiently and effectively.
• This layer manages the abstract data structures and allows high-level data structures (example- banking records), which are to be defined or exchanged.
• This layer carries out the encryption at the transmitter and decryption at the receiver.
• This layer carries out data compression to reduce the bandwidth of the data to be transmitted (the primary goal of data compression is to reduce the number of bits which is to be transmitted).
• This layer is responsible for interoperability (ability of computers to exchange and make use of information) between encoding methods as different computers use different encoding methods.
• This layer basically deals with the presentation part of the data.
• Presentation layer, carries out the data compression (number of bits reduction while transmission), which in return improves the data throughput.
• This layer also deals with the issues of string representation.
• The presentation layer is also responsible for integrating all the formats into a standardized format for efficient and effective communication.
• This layer encodes the message from the user-dependent format to the common format and vice-versa for communication between dissimilar systems.
• This layer deals with the syntax and semantics of the messages.
• This layer also ensures that the messages which are to be presented to the upper as well as the lower layer should be standardized as well as in an accurate format too.
• Presentation layer is also responsible for translation, formatting, and delivery of information for processing or display.
• This layer also performs serialization (process of translating a data structure or an object into a format that can be stored or transmitted easily).

Features of Presentation Layer in the OSI model: Presentation layer, being the 6th layer in the OSI model, plays a vital role while communication is taking place between two devices in a network.

List of features which are provided by the presentation layer are:

• Presentation layer could apply certain sophisticated compression techniques, so fewer bytes of data are required to represent the information when it is sent over the network.
• If two or more devices are communicating over an encrypted connection, then this presentation layer is responsible for adding encryption on the sender’s end as well as the decoding the encryption on the receiver’s end so that it can represent the application layer with unencrypted, readable data.
• This layer formats and encrypts data to be sent over a network, providing freedom from compatibility problems.
• This presentation layer also negotiates the Transfer Syntax.
• This presentation layer is also responsible for compressing data it receives from the application layer before delivering it to the session layer (which is the 5th layer in the OSI model) and thus improves the speed as well as the efficiency of communication by minimizing the amount of the data to be transferred.

Working of Presentation Layer in the OSI model : Presentation layer in the OSI model, as a translator, converts the data sent by the application layer of the transmitting node into an acceptable and compatible data format based on the applicable network protocol and architecture.  Upon arrival at the receiving computer, the presentation layer translates data into an acceptable format usable by the application layer. Basically, in other words, this layer takes care of any issues occurring when transmitted data must be viewed in a format different from the original format. Being the functional part of the OSI mode, the presentation layer performs a multitude (large number of) data conversion algorithms and character translation functions. Mainly, this layer is responsible for managing two network characteristics: protocol (set of rules) and architecture.

Presentation Layer Protocols : Presentation layer being the 6th layer, but the most important layer in the OSI model performs several types of functionalities, which makes sure that data which is being transferred or received should be accurate or clear to all the devices which are there in a closed network. Presentation Layer, for performing translations or other specified functions, needs to use certain protocols which are defined below –

• Apple Filing Protocol (AFP): Apple Filing Protocol is the proprietary network protocol (communications protocol) that offers services to macOS or the classic macOS. This is basically the network file control protocol specifically designed for Mac-based platforms.
• Lightweight Presentation Protocol (LPP): Lightweight Presentation Protocol is that protocol which is used to provide ISO presentation services on the top of TCP/IP based protocol stacks.
• NetWare Core Protocol (NCP): NetWare Core Protocol is the network protocol which is used to access file, print, directory, clock synchronization, messaging, remote command execution and other network service functions.
• Network Data Representation (NDR): Network Data Representation is basically the implementation of the presentation layer in the OSI model, which provides or defines various primitive data types, constructed data types and also several types of data representations.
• External Data Representation (XDR): External Data Representation (XDR) is the standard for the description and encoding of data. It is useful for transferring data between computer architectures and has been used to communicate data between very diverse machines. Converting from local representation to XDR is called encoding, whereas converting XDR into local representation is called decoding.
• Secure Socket Layer (SSL): The Secure Socket Layer protocol provides security to the data that is being transferred between the web browser and the server. SSL encrypts the link between a web server and a browser, which ensures that all data passed between them remains private and free from attacks.

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:cake :Layered Architecture

Layered Architecture is a software design pattern that is widely used in modern software development. It is a logical and structured approach to software design that separates different functional modules of an application into four separate horizontal layers, each with a specific set of responsibilities. This separation of concerns makes the code more modular, maintainable, and scalable, and enables easier testing and debugging.

This particular architectural pattern has influenced the development of various other architectural patterns, including:

• Hexagonal Architecture (also known as Ports and Adapters)
• Onion Architecture
• Clean Architecture

These patterns have emerged in response to the need to clarify further the concept of layered architecture, and they have each added their own unique features and benefits. However, all these patterns have in common the goal to provide a more modular, flexible, and maintainable approach to building software systems.

Therefore, we strongly recommend understanding the core principles of layered architecture and its relationship to these other patterns, as it will help you better understand these other software architecture patterns, and help you make informed decisions about which approach is best suited to your specific needs and requirements.

In this article, we will focus on the over-arching Layered Architecture , explaining its key principles, benefits, and implementation strategies. We will also discuss some real-world examples of successful implementation and highlight the advantages of using Layered Architecture in modern software development.

What exactly is layered architecture?

Layered architecture is a common pattern used in software design, where the application is divided into different layers based on their functionality. In a four-layered architecture, the layers are typically divided into:

• Presentation
• Application
• Infrastructure

These layers are arranged in a hierarchical order, where each layer provides services to the layer above it and uses services from the layer below it, and each layer is responsible for handling specific tasks and has limited communication with the other layers.

This helps to improve modularity and allows for better separation of concerns. The architecture is called "layered" because it resembles a layered cake, where each layer is independent of the others but builds on them to form a complete and cohesive application.

• Presentation Layer

The presentation layer is the topmost layer of the architecture, responsible for handling the user interface and displaying data to the user. This layer interacts with the application layer to retrieve the data and provides a visual representation of the data to the user. In web applications, this layer is often implemented using HTML, CSS, and JavaScript.

• Application Layer

The application layer is responsible for handling business logic and coordinating interactions between different components. This layer receives input from the presentation layer and processes it before passing it down to the domain layer. It is also responsible for communicating with external systems and services. Think of this layer as the maestro in an orchestra, that guides the musicians on what, when and how to play their instrument, but who doesn't actually play any instrument himself. Similarly, the Application Layer doesn't do anything per se, but it tells the domain layer what and when it should do something.

• Domain Layer

The domain layer contains the business logic and rules of the application. This layer represents the core of the application and defines how the application processes data and interacts with the external world. It is responsible for ensuring the consistency and validity of the data and defines the behavior of the application. Here is where you'll find the algorithms, the programming compoenents, the functions, etc. Its really the heart of the application and generally what adds most value to the application itself.

• Infrastructure Layer

The infrastructure layer is responsible for handling external dependencies and providing services to the other layers. This layer interacts with databases, file systems, and other external systems. It also provides services such as logging, caching, and authentication to the other layers. By separating infrastructure concerns from the rest of the application, it becomes easier to maintain and replace external dependencies without affecting the core functionality of the application.

• Advantages of Layered Architecture

Layered architecture offers several advantages that make it a popular choice for large and complex software systems.

Modular structure: By dividing the application into different layers, developers can isolate specific functionalities and easily modify or replace them without affecting other parts of the system. This allows for more agile development and easier maintenance.

Separation of concerns: Each layer is responsible for a specific set of tasks, and there is limited communication between the layers. This helps to ensure that the code is organized and easy to understand, making it easier to test and debug. This ensures a clear separation of the application's functionality and the underlying technology, allowing for better scalability, as additional layers can be added to handle increased functionality without affecting the existing layers.

For example, the presentation layer can be implemented using different technologies, such as a web-based user interface or a mobile app, without affecting the business or data access layers. This flexibility makes it easier to adapt the application to different environments or requirements.

• Code reusability: Because each layer has a well-defined interface, it is possible to reuse code across different applications or even different layers of the same application. This can save developers time and effort by reducing the amount of code they need to write and maintain.

In large and complex software systems, layered architecture is particularly important. These systems often involve multiple teams of developers working on different parts of the system simultaneously. Layered architecture helps to promote modularity and separation of concerns, making it easier for teams to work independently without stepping on each other's toes. It also makes it easier to manage and maintain the codebase over time, as the structure of the system is well-defined and easy to understand.

Additionally, layered architecture helps to ensure that the system remains robust and reliable. By dividing the application into different layers, developers can focus on specific functionalities and ensure that they are working correctly. This helps to reduce the likelihood of bugs or errors that could cause the system to fail. It also makes it easier to identify and fix issues when they do occur, as the problem is likely to be isolated to a specific layer rather than affecting the entire system.

• Implementing Layered Architecture

Implementing Layered Architecture involves defining the interfaces and responsibilities of each layer and the interactions between them. Here are some steps to follow when implementing Layered Architecture:

Define the layers: Identify the different layers of the application and their responsibilities. The layers should be as independent as possible, with clear and well-defined interfaces. A good practice is to use a dependency injection framework to manage the dependencies between the layers.

Implement the layers: Develop the classes and functions that implement the functionality of each layer. The classes should only interact with the layer above or below them and should not depend on other layers. Each layer should have its own set of tests to ensure its functionality and integration with the other layers.

Define the interfaces: Define the interfaces between the layers, specifying the methods and parameters that each layer requires from the layer below it. The interfaces should be simple and focused on the specific needs of each layer. The interfaces should be designed to be easy to use, easy to understand, and easy to test.

Handle exceptions: Define how exceptions will be handled between the layers. A good practice is to catch exceptions in the lower layers and convert them to more specific exceptions in the higher layers. This approach helps to keep the application logic separated from the exception handling logic and facilitates debugging.

Test and validate the layers: Once the layers are implemented, test them individually and in combination. Validate that the layers work correctly, that the interfaces are well defined and easy to use, and that the application behaves as expected.

Monitor and maintain the layers: Once the application is in production, monitor and maintain the layers. Ensure that the layers are stable, scalable, and secure. Make any necessary changes to the layers to optimize performance, improve security, or fix bugs.

In summary, implementing a layered architecture is definitely a bit more work than simply not thinking about this, however, its very clear that most developers follow a similar thought process when starting a new project. Therefore, its worth investing just a bit more time into this design process as it will help you build better quality software going forward.

• Use cases and real-world examples

There are numerous real-world examples of successful implementations of Layered Architecture in various organizations. One such example is the Apache Struts framework, which is widely used for building Java-based web applications. The Struts framework uses a three-layered architecture that separates the presentation, business logic, and data access layers. This has made it easier for developers to maintain and extend the framework, as well as to customize it to meet specific business requirements.

Another example is the Spring framework, which is also widely used for building Java-based web applications. The Spring framework uses a four-layered architecture that includes a presentation layer, a business logic layer, a persistence layer, and a data access layer. This layered approach has made it easier for developers to build scalable, robust, and flexible web applications that can handle large volumes of traffic and complex business logic.

Organizations that have adopted Layered Architecture have benefited from several advantages. Firstly, this approach provides a clear separation of concerns between different layers, which makes it easier to manage complexity and maintainability in larger, more complex software systems. This separation of concerns also allows developers to work more efficiently, as they can focus on specific areas of the application without worrying about the impact on other parts of the system.

Secondly, Layered Architecture enables organizations to achieve better performance and scalability in their software systems. By separating the business logic and data access layers, for example, organizations can optimize each layer for specific performance requirements and improve the overall efficiency of the system.

Lastly, Layered Architecture also supports better reusability and flexibility in software systems. By encapsulating functionality within separate layers, organizations can more easily reuse and extend different components of the system without impacting other parts of the architecture. This can help organizations to build more modular and maintainable software systems that can adapt to changing business requirements over time.

Layered architecture is a fundamental software design pattern that provides a clear separation of concerns and promotes modularity and flexibility in software systems. It allows for the development of robust, scalable, and maintainable applications that can adapt to changing business requirements.

Through understanding the principles and benefits of layered architecture, developers can effectively implement this pattern in their own software projects. With the clear separation of concerns, each layer can be developed and maintained independently, allowing for better code reuse, easier testing, and overall improved software quality.

The importance of using layered architecture in modern software development cannot be overstated. As software systems become increasingly complex, layered architecture provides a scalable and adaptable approach to designing and maintaining such systems. It is a proven methodology that has been successfully implemented in many real-world scenarios.

We encourage developers to start implementing layered architecture in their own software projects. By doing so, they can reap the many benefits that this design pattern has to offer, including improved software quality, easier maintenance, and increased scalability. With careful planning and implementation, layered architecture can be a powerful tool in the development of successful software systems.

• Additional resources

Here are a few additional references with regards to Layered Architecture:

• The Layered Architecture Pattern in Software Architecture - Article by Kayvan Kaseb
• Layered Architecture - Article by Herberto Graça
• Software Architecture Patterns — Layered Architecture - Article by Priyal Walpita

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Breaking Down the Layers: Understanding the Four-tier Software Architecture

Table of Contents

Introduction to four-tier software architecture, benefits and advantages of four-tier software architecture, key components and layers in four-tier software architecture, best practices for implementing four-tier software architecture.

Unveiling the Essence: Decoding Four-tier Software Architecture

Software architecture is a crucial aspect of any software development project. It provides a blueprint for designing and organizing the various components of a software system. One popular approach to software architecture is the four-tier architecture, which divides the system into four distinct layers . In this article, we will delve into the world of four-tier software architecture, exploring its components and benefits.

At its core, four-tier software architecture is a client-server model that separates the user interface, business logic, data storage, and data access layers. Each layer has a specific role and interacts with the other layers in a well-defined manner. This separation of concerns allows for better scalability, maintainability, and flexibility in software development.

The first layer of the four-tier architecture is the presentation layer, also known as the user interface layer. This layer is responsible for presenting information to the user and receiving user input. It includes components such as web pages, forms, and graphical user interfaces. The presentation layer communicates with the business logic layer to retrieve and display data to the user.

Moving down the architecture, we come to the business logic layer. This layer contains the core functionality of the software system. It processes user requests, performs calculations, and enforces business rules. The business logic layer acts as the intermediary between the presentation layer and the data access layer, ensuring that data is retrieved and manipulated correctly.

Next, we have the data access layer. This layer is responsible for interacting with the database or any other data storage mechanism. It handles tasks such as retrieving, updating, and deleting data. The data access layer abstracts the underlying data storage technology, allowing the other layers to work with data in a consistent manner. It provides a level of separation between the business logic layer and the data storage layer, making it easier to switch databases or make changes to the data storage mechanism.

Finally, we reach the data storage layer, which is where the actual data is stored. This layer can consist of a relational database, a file system, or any other data storage technology. The data storage layer is responsible for ensuring data integrity, security, and availability. It is accessed by the data access layer to retrieve and store data.

Now that we have a basic understanding of the four-tier software architecture, let's explore its benefits. One of the main advantages of this architecture is its modularity. Each layer can be developed and maintained independently, allowing for easier testing, debugging, and updates. Changes made to one layer do not necessarily affect the other layers, reducing the risk of unintended consequences.

Another benefit is scalability. The four-tier architecture allows for horizontal scaling, meaning that additional servers can be added to handle increased user load. This scalability is achieved by distributing the workload across multiple servers, with each server responsible for a specific layer. This distributed approach improves performance and ensures that the system can handle a growing number of users.

Additionally, the four-tier architecture promotes reusability. By separating the different layers, developers can reuse components across multiple projects. For example, the business logic layer can be reused in different user interfaces or with different data storage mechanisms. This reusability saves time and effort in software development, leading to faster delivery and reduced costs.

In conclusion, the four-tier software architecture provides a structured approach to software development, dividing the system into four distinct layers. Each layer has a specific role and interacts with the other layers in a well-defined manner. This architecture offers benefits such as modularity, scalability, and reusability. By understanding and implementing the four-tier architecture, software developers can create robust and flexible systems that meet the needs of their users.

One of the key advantages of four-tier software architecture is its ability to enhance scalability and flexibility. By separating the software into different layers, it becomes easier to modify or replace one layer without affecting the others. This modular approach allows for more efficient development and maintenance, as changes can be made to specific layers without disrupting the entire system. This flexibility is particularly valuable in large-scale software projects where multiple teams are working simultaneously on different components.

Another benefit of four-tier software architecture is improved performance and efficiency. By distributing the workload across multiple layers, the system can handle a higher volume of requests and process them more quickly. For example, the presentation layer, which is responsible for user interaction, can focus solely on rendering the user interface and handling user input, while the business logic layer handles the processing and manipulation of data. This division of labor ensures that each layer can perform its tasks efficiently, resulting in a more responsive and performant software system.

Furthermore, four-tier software architecture promotes reusability and maintainability. With clear separation between layers, developers can reuse components across different projects or even within the same project. This not only saves time and effort but also improves the overall quality of the software. Additionally, the modular nature of this architecture makes it easier to test and debug individual layers, simplifying the maintenance and troubleshooting process. This reduces the risk of introducing new bugs or issues when making changes to the software.

Security is another area where four-tier software architecture excels. By isolating sensitive data and logic in separate layers, it becomes easier to implement security measures at each level. For example, the data layer can enforce strict access controls and encryption mechanisms to protect the integrity and confidentiality of the data. Similarly, the business logic layer can implement authentication and authorization mechanisms to ensure that only authorized users can access certain functionalities. This layered approach to security minimizes the risk of unauthorized access or data breaches, making the software more robust and secure.

Lastly, four-tier software architecture promotes collaboration and teamwork. With clear boundaries between layers, different teams or individuals can work independently on their assigned layers, without stepping on each other's toes. This promotes parallel development and allows for more efficient collaboration, as teams can focus on their specific areas of expertise. Moreover, the modular nature of this architecture facilitates integration with external systems or third-party components, enabling seamless collaboration with external stakeholders.

In conclusion, four-tier software architecture offers numerous benefits and advantages that make it a popular choice in the development of complex software systems. From enhanced scalability and flexibility to improved performance and efficiency, this architecture promotes reusability, maintainability, security, and collaboration. By understanding and leveraging the advantages of four-tier software architecture, developers can build robust, scalable, and maintainable software systems that meet the evolving needs of businesses and users alike.

In the world of software development, architects and developers often rely on different architectural patterns to design and build robust and scalable applications. One such pattern is the four-tier software architecture, which provides a structured approach to organizing the various components of a software system. Understanding the key components and layers in this architecture is crucial for developers looking to build efficient and maintainable applications.

At its core, the four-tier software architecture consists of four distinct layers: the presentation layer, the application layer, the business logic layer, and the data layer. Each layer has its own set of responsibilities and interacts with the layers above and below it in a well-defined manner.

The presentation layer, also known as the user interface layer, is the layer that users directly interact with. It is responsible for presenting information to the user and capturing user input. This layer typically includes components such as web pages, mobile app screens, and user input forms. Its primary goal is to provide a user-friendly interface that allows users to interact with the application easily.

Moving down the stack, we come to the application layer. This layer acts as a bridge between the presentation layer and the business logic layer. It handles user requests, processes them, and coordinates the flow of data between the presentation layer and the business logic layer. In simpler terms, it acts as a mediator, ensuring that the user's actions are translated into meaningful operations that the business logic layer can understand.

The business logic layer, also known as the application layer, is where the core functionality of the software resides. It contains the business rules, algorithms, and workflows that define how the application operates. This layer is responsible for processing data, performing calculations, and enforcing business rules. It acts as the brain of the application, making decisions and orchestrating the overall behavior of the system.

Finally, we have the data layer, which is responsible for managing the storage and retrieval of data. This layer interacts with databases, file systems, or any other data storage mechanism used by the application. It handles tasks such as reading and writing data, querying databases, and ensuring data integrity. The data layer plays a critical role in ensuring that the application can store and retrieve data efficiently and reliably.

Understanding the interactions between these layers is crucial for building a well-structured and maintainable software system. Each layer has its own set of responsibilities, and they work together to create a cohesive and efficient application. For example, the presentation layer interacts with the application layer to handle user input and display information to the user. The application layer, in turn, interacts with the business logic layer to process user requests and enforce business rules. Finally, the business logic layer interacts with the data layer to store and retrieve data as needed.

By breaking down the software system into these distinct layers, developers can achieve a high degree of modularity and separation of concerns. Each layer can be developed and tested independently, making it easier to maintain and extend the application over time. Additionally, this architecture allows for scalability, as each layer can be scaled independently based on the specific needs of the application.

In conclusion, the four-tier software architecture provides a structured approach to organizing the components of a software system. Understanding the key components and layers in this architecture is crucial for developers looking to build efficient and maintainable applications. By breaking down the system into the presentation layer, application layer, business logic layer, and data layer, developers can achieve modularity, separation of concerns, and scalability. So, the next time you embark on a software development project, consider leveraging the power of the four-tier software architecture to build robust and scalable applications.

In today's digital age, software architecture plays a crucial role in the development and implementation of complex applications. One popular approach to software architecture is the four-tier architecture, which provides a structured and scalable framework for building robust software systems. In this article, we will delve into the best practices for implementing four-tier software architecture, breaking down each layer and exploring its purpose and benefits.

The first layer of the four-tier architecture is the presentation layer. This layer is responsible for handling the user interface and interaction with the application. It focuses on providing a seamless and intuitive user experience, ensuring that the application is visually appealing and easy to navigate. By separating the presentation layer from the other layers, developers can make changes to the user interface without affecting the underlying business logic. This layer also enables the use of different presentation technologies, such as web or mobile, depending on the requirements of the application.

Moving on to the second layer, we have the application layer. This layer acts as the bridge between the presentation layer and the business logic layer. It handles the processing of user requests, validates input data, and coordinates the flow of information between the presentation and business logic layers. By encapsulating these responsibilities in a separate layer, developers can ensure that the application remains modular and maintainable. Additionally, the application layer enables the implementation of business rules and logic, making it easier to modify and extend the functionality of the application.

Next, we have the business logic layer, which forms the core of the application. This layer is responsible for implementing the business rules and processes that drive the application's functionality. It handles complex calculations, data validation, and database operations. By separating the business logic from the other layers, developers can ensure that the application remains flexible and scalable. This layer also promotes code reusability, as the business logic can be shared across multiple applications or modules.

Finally, we have the data access layer, which is responsible for interacting with the underlying data storage systems, such as databases or external APIs. This layer handles the retrieval, storage, and manipulation of data, ensuring that the application has access to the necessary information. By separating the data access logic from the other layers, developers can easily switch between different data sources or make changes to the database schema without affecting the rest of the application. This layer also improves performance by optimizing data retrieval and minimizing network latency.

Implementing four-tier software architecture requires careful planning and adherence to best practices. One important aspect is the separation of concerns, where each layer focuses on a specific set of responsibilities. This separation enables modularity, maintainability, and scalability, making it easier to develop and evolve the application over time. Additionally, developers should strive for loose coupling between the layers, minimizing dependencies and promoting code reusability.

Another best practice is the use of well-defined interfaces between the layers. This allows for easy integration and testing, as each layer can be developed and tested independently. It also promotes interoperability, as different layers can be implemented using different technologies or programming languages. By adhering to these best practices, developers can ensure that the four-tier software architecture is implemented effectively and efficiently.

In conclusion, understanding the four-tier software architecture is essential for building robust and scalable applications. By breaking down each layer and exploring its purpose and benefits, developers can gain a deeper understanding of how the architecture works and how to implement it effectively. By following best practices such as separation of concerns and well-defined interfaces, developers can ensure that their applications are modular, maintainable, and scalable. So, whether you are a seasoned developer or just starting your journey in software architecture, the four-tier architecture is definitely worth exploring.

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  Layer 6 Presentation Layer

De/Encryption, Encoding, String representation

The presentation layer (data presentation layer, data provision level) sets the system-dependent representation of the data (for example, ASCII, EBCDIC) into an independent form, enabling the syntactically correct data exchange between different systems. Also, functions such as data compression and encryption are guaranteed that data to be sent by the application layer of a system that can be read by the application layer of another system to the layer 6. The presentation layer. If necessary, the presentation layer acts as a translator between different data formats, by making an understandable for both systems data format, the ASN.1 (Abstract Syntax Notation One) used.

OSI Layer 6 - Presentation Layer

The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service would be the conversion of an EBCDIC-coded text computer file to an ASCII-coded file. The presentation layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in the form of datagrams or packets between hosts. This layer deals with issues of string representation - whether they use the Pascal method (an integer length field followed by the specified amount of bytes) or the C/C++ method (null-terminated strings, e.g. "thisisastring\0"). The idea is that the application layer should be able to point at the data to be moved, and the presentation layer will deal with the rest. Serialization of complex data structures into flat byte-strings (using mechanisms such as TLV or XML) can be thought of as the key functionality of the presentation layer. Encryption is typically done at this level too, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages. Decryption is also handled at the presentation layer. For example, when logging on to bank account sites the presentation layer will decrypt the data as it is received.[1] Another example is representing structure, which is normally standardized at this level, often by using XML. As well as simple pieces of data, like strings, more complicated things are standardized in this layer. Two common examples are 'objects' in object-oriented programming, and the exact way that streaming video is transmitted. In many widely used applications and protocols, no distinction is made between the presentation and application layers. For example, HyperText Transfer Protocol (HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify character encoding for proper conversion, which is then done in the application layer. Within the service layering semantics of the OSI network architecture, the presentation layer responds to service requests from the application layer and issues service requests to the session layer. In the OSI model: the presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer might be able to translate between multiple data formats by using a common format. Wikipedia

• Data conversion
• Character code translation
• Compression
• Encryption and Decryption

The Presentation OSI Layer is usually composed of 2 sublayers that are:

CASE common application service element

SASE specific application service element

Layer 7   Application Layer

Layer 6   presentation layer, layer 5   session layer, layer 4   transport layer, layer 3   network layer, layer 2   data link layer, layer 1   physical layer.

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Posted on Apr 12, 2023 • Updated on Jun 14, 2023

Layered Architecture Used in Software Development

Introduction:.

Large-scale applications frequently use the well-liked software design paradigm known as layered architecture. It is a structural layout that separates the system into various levels, each of which is in charge of carrying out particular duties. Four layers make up the layered architecture: presentation, application, domain, and infrastructure. Each layer interacts with the layers above and below it and has a distinct role to play. As a result of the separation of concerns made possible by the layered architecture, the system is more modular, testable, and maintainable. The creation of complex applications depends heavily on software architecture. A system's maintainability, scalability, and reliability can all be increased by a well-designed architecture. Layered architecture is one of the most widely used architectural patterns because it effectively isolates concerns and encourages versatility. We will go into great detail on layered architecture in this essay, including its advantages, ways to use it, and recommended practices.

What is Layered Architecture?

With layered architecture, the system is divided into a number of layers, each of which is responsible for a different task and interacts with the layers above and below it. This design pattern encourages modularity, concern separation, and flexibility, which makes the system simpler to test, maintain, and grow. Four layers make up the layered architecture: presentation, application, domain, and infrastructure. Each layer is in charge of a certain task and only interacts with the layers directly above and below it. The system becomes more modular and is simpler to test and maintain because to this pattern's ability to clearly separate concerns.

Presentation Layer

The system's top layer, the presentation layer, is in charge of managing user interactions. It deals with data presentation, user input validation, and user interface. To retrieve and store data, this layer interfaces with the application layer. A desktop application, a mobile application, or a web interface can all be used to implement the presentation layer.

Application Layer

The application layer serves as a bridge between the presentation and domain layers by sitting between them. It controls data flow between the presentation and domain levels, handles user requests, and executes business logic. Security and permission rules must be implemented at this layer as well. Application layer implementations can take the form of a collection of RESTful web services or a collection of API endpoints.

Domain Layer

The application's core, the domain layer, houses the entities, business logic, and data access rules. The management of the system's state and the enforcement of business rules are under the purview of this layer. It doesn't interact with the presentation layer and solely talks to the application layer. As a collection of classes, interfaces, and data access objects, the domain layer can be put into practice.

Infrastructure Layer

The infrastructure layer is the system's lowest layer and is in charge of managing the system's resources, including the file system, database, and network connections. It implements technical concerns like logging, caching, and speed optimization while also providing services to the other layers. Both a collection of libraries and a collection of microservices can be used to implement this tier.

Advantages of Layered Architecture

Separation of concerns:.

The system's testing and maintenance are simplified by the layered architecture's obvious concern separation.

Modularity:

It is simpler to scale and reuse components across several levels and applications since each layer may be built and tested independently of the others.

Flexibility:

Scalability:.

The infrastructure layer may be easily scaled horizontally by adding additional instances.

Reusability:

Because components may be reused between layers and applications, the layered architecture speeds up development and lowers costs.

Implementation of Layered Architecture

• The system-specific requirements determine how the layered architecture pattern should be implemented. The following are some best practices for layered architecture implementation:
• Establish distinct roles for each tier. Each layer ought to oversee a certain task and only communicate with layers that are directly above and below it.
• Interact between levels using interfaces: It is simpler to build and test each layer independently when there is a clear contract between the layers thanks to interfaces.
• Manage dependencies with dependency injection: Separating concerns is possible thanks to dependency injection, which also makes system testing and maintenance simpler.

Advantages of Layered Architecture:

• The system is simpler to test and maintain because to its modular design and separation of concerns. • It is possible to build and test each layer separately from the others. • The infrastructure layer may be easily scaled horizontally by adding additional instances. • Component reuse across layers and applications is made possible by the tiered design. • Because of the layered architecture, developers may concentrate on their area of expertise, which increases productivity and improves code quality.

Dis-Advantages of Layered Architecture:

A common software architectural pattern called "layered architecture" divides an application into logical layers, each of which offers a specific set of services and functionalities to the layer above it. While employing a layered design has many benefits, there are a few drawbacks to take into account as well:

Performance Overhead:

Due to the additional layers of indirection and abstraction, layered architectures may result in performance overhead. Prior to data being passed to the next layer, each layer must complete its processing, which can cause an increase in latency and a decrease in performance.

Tight Coupling:

A layered design can result in close coupling between levels, making it challenging to change or remove individual layers without impacting the system as a whole. This may result in expensive maintenance fees and limited flexibility.

Scalability Challenges:

Scalability issues can arise in layered designs, particularly if the layers are not appropriately built to withstand high traffic levels. This issue can be made worse by adding more layers, which will result in further performance and scalability problems.

Complexity:

Particularly when the number of layers rises, layered systems can become complex and challenging to comprehend. The system may become difficult to extend and maintain as a result.

Communication Overhead:

Conclusion:.

The layered architecture is a popular paradigm for software architecture that encourages modularity, scalability, and maintainability while explicitly separating domains. It consists of four layers: infrastructure, presentation, application, and domain. Each layer has a distinct function and only communicates with the layer directly above and below it.

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Application Architecture Guide - Chapter 10 - Presentation Layer Guidelines

Note - The patterns & practices Microsoft Application Architecture Guide, 2nd Edition is now live at http://msdn.microsoft.com/en-us/library/dd673617.aspx .

- J.D. Meier, Alex Homer, David Hill, Jason Taylor, Prashant Bansode, Lonnie Wall, Rob Boucher Jr, Akshay Bogawat

• 1 Objectives
• 3 Presentation Layer Components
• 5 Design Considerations
• 6 Presentation Layer Frame
• 8 Composition
• 9 Exception Management
• 12 Navigation
• 13 Presentation Entities
• 14 Request Processing
• 15 User Experience
• 16 UI Components
• 17 UI Process Components
• 18 Validation
• 19 Pattern Map
• 20 Pattern Descriptions
• 21.1 Mobile Applications
• 21.2 Rich Client Applications
• 21.3 Rich Internet Applications (RIA)
• 21.4 Web Applications
• 22 patterns & practices Solution Assets
• 23 Additional Resources
• Understand how the presentation layer fits into typical application architecture.
• Understand the components of the presentation layer.
• Learn the steps for designing the presentation layer.
• Learn the common issues faced while designing the presentation layer.
• Learn the key guidelines for designing the presentation layer.
• Learn the key patterns and technology considerations for designing the presentation layer.

The presentation layer contains the components that implement and display the user interface and manage user interaction. This layer includes controls for user input and display, in addition to components that organize user interaction. Figure 1 shows how the presentation layer fits into a common application architecture.

Figure 1 A typical application showing the presentation layer and the components it may contain

Presentation Layer Components

• User interface (UI) components . User interface components provide a way for users to interact with the application. They render and format data for users. They also acquire and validate data input by the user.
• User process components . User process components synchronize and orchestrate user interactions. Separate user process components may be useful if you have a complicated UI. Implementing common user interaction patterns as separate user process components allows you to reuse them in multiple UIs.

The following steps describe the process you should adopt when designing the presentation layer for your application. This approach will ensure that you consider all of the relevant factors as you develop your architecture:

• Identify your client type . Choose a client type that satisfies your requirements and adheres to the infrastructure and deployment constraints of your organization. For instance, if your users are on mobile devices and will be intermittently connected to the network, a mobile rich client is probably your best choice.
• Determine how you will present data . Choose the data format for your presentation layer and decide how you will present the data in your UI.
• Determine your data-validation strategy . Use data-validation techniques to protect your system from untrusted input.
• Determine your business logic strategy . Factor out your business logic to decouple it from your presentation layer code.
• Determine your strategy for communication with other layers . If your application has multiple layers, such as a data access layer and a business layer, determine a strategy for communication between your presentation layer and other layers.

Design Considerations

There are several key factors that you should consider when designing your presentation layer. Use the following principles to ensure that your design meets the requirements for your application, and follows best practices:

• Choose the appropriate UI technology. Determine if you will implement a rich (smart) client, a Web client, or a rich Internet application (RIA). Base your decision on application requirements, and on organizational and infrastructure constraints.
• Use the relevant patterns. Review the presentation layer patterns for proven solutions to common presentation problems.
• Design for separation of concerns. Use dedicated UI components that focus on rendering and display. Use dedicated presentation entities to manage the data required to present your views. Use dedicated UI process components to manage the processing of user interaction.
• Consider human interface guidelines. Review your organization’s guidelines for UI design. Review established UI guidelines based on the client type and technologies that you have chosen.
• Adhere to user-driven design principles. Before designing your presentation layer, understand your customer. Use surveys, usability studies, and interviews to determine the best presentation design to meet your customer’s requirements.

Presentation Layer Frame

There are several common issues that you must consider as your develop your design. These issues can be categorized into specific areas of the design. The following table lists the common issues for each category where mistakes are most often made.

Table 1 Presentation Layer Frame

Caching is one of the best mechanisms you can use to improve application performance and UI responsiveness. Use data caching to optimize data lookups and avoid network round trips. Cache the results of expensive or repetitive processes to avoid unnecessary duplicate processing.

Consider the following guidelines when designing your caching strategy:

• Do not cache volatile data.
• Consider using ready-to-use cache data when working with an in-memory cache. For example, use a specific object instead of caching raw database data.
• Do not cache sensitive data unless you encrypt it.
• If your application is deployed in Web farm, avoid using local caches that need to be synchronized; instead, consider using a transactional resource manager such as Microsoft SQL Server® or a product that supports distributed caching.
• Do not depend on data still being in your cache. It may have been removed.

Composition

Consider whether your application will be easier to develop and maintain if the presentation layer uses independent modules and views that are easily composed at run time. Composition patterns support the creation of views and the presentation layout at run time. These patterns also help to minimize code and library dependencies that would otherwise force recompilation and redeployment of a module when the dependencies change. Composition patterns help you to implement sharing, reuse, and replacement of presentation logic and views.

Consider the following guidelines when designing your composition strategy:

• Avoid using dynamic layouts. They can be difficult to load and maintain.
• Be careful with dependencies between components. For example, use abstraction patterns when possible to avoid issues with maintainability.
• Consider creating templates with placeholders. For example, use the Template View pattern to compose dynamic Web pages in order to ensure reuse and consistency.
• Consider composing views from reusable modular parts. For example, use the Composite View pattern to build a view from modular, atomic component parts.
• If you need to allow communication between presentation components, consider implementing the Publish/Subscribe pattern. This will lower the coupling between the components and improve testability.

Exception Management

Design a centralized exception-management mechanism for your application that catches and throws exceptions consistently. Pay particular attention to exceptions that propagate across layer or tier boundaries, as well as exceptions that cross trust boundaries. Design for unhandled exceptions so they do not impact application reliability or expose sensitive information.

Consider the following guidelines when designing your exception management strategy:

• Use user-friendly error messages to notify users of errors in the application.
• Avoid exposing sensitive data in error pages, error messages, log files, and audit files.
• Design a global exception handler that displays a global error page or an error message for all unhandled exceptions.
• Differentiate between system exceptions and business errors. In the case of business errors, display a user-friendly error message and allow the user to retry the operation. In the case of system exceptions, check to see if the exception was caused by issues such as system or database failure, display a user-friendly error message, and log the error message, which will help in troubleshooting.
• Avoid using exceptions to control application logic.

Design a user input strategy based on your application input requirements. For maximum usability, follow the established guidelines defined in your organization, and the many established industry usability guidelines based on years of user research into input design and mechanisms.

Consider the following guidelines when designing your input collection strategy:

• Use forms-based input controls for normal data-collection tasks.
• Use a document-based input mechanism for collecting input in Microsoft Office–style documents.
• Implement a wizard-based approach for more complex data collection tasks, or for input that requires a workflow.
• Design to support localization by avoiding hard-coded strings and using external resources for text and layout.
• Consider accessibility in your design. You should consider users with disabilities when designing your input strategy; for example, implement text-to-speech software for blind users, or enlarge text and images for users with poor sight. Support keyboard-only scenarios where possible for users who cannot manipulate a pointing device.

Design your UI layout so that the layout mechanism itself is separate from the individual UI components and UI process components. When choosing a layout strategy, consider whether you will have a separate team of designers building the layout, or whether the development team will create the UI. If designers will be creating the UI, choose a layout approach that does not require code or the use of development-focused tools.

Consider the following guidelines when designing your layout strategy:

• Use templates to provide a common look and feel to all of the UI screens.
• Use a common look and feel for all elements of your UI to maximize accessibility and ease of use.
• Consider device-dependent input, such as touch screens, ink, or speech, in your layout. For example, with touch-screen input you will typically use larger buttons with more spacing between them than you would with mouse or keyboard inputs.
• When building a Web application, consider using Cascading Style Sheets (CSS) for layout. This will improve rendering performance and maintainability.
• Use design patterns, such as Model-View-Presenter (MVP), to separate the layout design from interface processing.

Design your navigation strategy so that users can navigate easily through your screens or pages, and so that you can separate navigation from presentation and UI processing. Ensure that you display navigation links and controls in a consistent way throughout your application to reduce user confusion and hide application complexity.

Consider the following guidelines when designing your navigation strategy:

• Use well-known design patterns to decouple the UI from the navigation logic where this logic is complex.
• Design toolbars and menus to help users find functionality provided by the UI.
• Consider using wizards to implement navigation between forms in a predictable way.
• Determine how you will preserve navigation state if the application must preserve this state between sessions.
• Consider using the Command Pattern to handle common actions from multiple sources.

Presentation Entities

Use presentation entities to store the data you will use in your presentation layer to manage your views. Presentation entities are not always necessary; use them only if your datasets are sufficiently large and complex to require separate storage from the UI controls.

Consider the following guidelines when designing presentation entities:

• Determine if you require presentation entities. Typically, you may require presentation entities only if the data or the format to be displayed is specific to the presentation layer.
• If you are working with data-bound controls, consider using custom objects, collections, or datasets as your presentation entity format.
• If you want to map data directly to business entities, use a custom class for your presentation entities.
• Do not add business logic to presentation entities.
• If you need to perform data type validation, consider adding it in your presentation entities.

Request Processing

Design your request processing with user responsiveness in mind, as well as code maintainability and testability.

Consider the following guidelines when designing request processing:

• Use asynchronous operations or worker threads to avoid blocking the UI for long-running actions.
• Avoid mixing your UI processing and rendering logic.
• Consider using the Passive View pattern (a variant of MVP) for interfaces that do not manage a lot of data.
• Consider using the Supervising Controller pattern (a variant of MVP) for interfaces that manage large amounts of data.

User Experience

Good user experience can make the difference between a usable and unusable application. Carry out usability studies, surveys, and interviews to understand what users require and expect from your application, and design with these results in mind.

Consider the following guidelines when designing for user experience:

• When developing a rich Internet application (RIA), avoid synchronous processing where possible.
• When developing a Web application, consider using Asynchronous JavaScript and XML (AJAX) to improve responsiveness and to reduce post backs and page reloads.
• Do not design overloaded or overly complex interfaces. Provide a clear path through the application for each key user scenario.
• Design to support user personalization, localization, and accessibility.
• Design for user empowerment. Allow the user to control how he or she interacts with the application, and how it displays data to them.

UI Components

UI components are the controls and components used to display information to the user and accept user input. Be careful not to create custom controls unless it is necessary for specialized display or data collection.

Consider the following guidelines when designing UI components:

• Take advantage of the data-binding features of the controls you use in the UI.
• Create custom controls or use third-party controls only for specialized display and data-collection tasks.
• When creating custom controls, extend existing controls if possible instead of creating a new control.
• Consider implementing designer support for custom controls to make it easier to develop with them.
• Consider maintaining the state of controls as the user interacts with the application instead of reloading controls with each action.

UI Process Components

UI process components synchronize and orchestrate user interactions. UI processing components are not always necessary; create them only if you need to perform significant processing in the presentation layer that must be separated from the UI controls. Be careful not to mix business and display logic within the process components; they should be focused on organizing user interactions with your UI.

Consider the following guidelines when designing UI processing components:

• Do not create UI process components unless you need them.
• If your UI requires complex processing or needs to talk to other layers, use UI process components to decouple this processing from the UI.
• Consider dividing UI processing into three distinct roles: Model, View, and Controller/Presenter, by using the MVC or MVP pattern.
• Avoid business rules, with the exception of input and data validation, in UI processing components.
• Consider using abstraction patterns, such as dependency inversion, when UI processing behavior needs to change based on the run-time environment.
• Where the UI requires complex workflow support, create separate workflow components that use a workflow system such as Windows Workflow or a custom mechanism.

Designing an effective input and data-validation strategy is critical to the security of your application. Determine the validation rules for user input as well as for business rules that exist in the presentation layer.

Consider the following guidelines when designing your input and data validation strategy:

• Validate all input data on the client side where possible to improve interactivity and reduce errors caused by invalid data.
• Do not rely on client-side validation only. Always use server-side validation to constrain input for security purposes and to make security-related decisions.
• Design your validation strategy to constrain, reject, and sanitize malicious input.
• Use the built-in validation controls where possible, when working with .NET Framework.
• In Web applications, consider using AJAX to provide real-time validation.

Pattern Map

Key patterns are organized by key categories, as detailed in the Presentation Layer Frame in the following table. Consider using these patterns when making design decisions for each category.

Table 2 Pattern Map

• For more information on the Page Cache pattern, see “Enterprise Solution Patterns Using Microsoft .NET” at http://msdn.microsoft.com/en-us/library/ms998469.aspx
• For more information on the Model-View-Controller (MVC), Page Controller, Front Controller, Template View, Transform View, and Two-Step View patterns, see “Patterns of Enterprise Application Architecture (P of EAA)” at http://martinfowler.com/eaaCatalog/
• For more information on the Composite View, Supervising Controller, and Presentation Model patterns, see “Patterns in the Composite Application Library” at http://msdn.microsoft.com/en-us/library/cc707841.aspx
• For more information on the Chain of responsibility and Command pattern, see “data & object factory” at http://www.dofactory.com/Patterns/Patterns.aspx
• For more information on the Asynchronous Callback pattern, see “Creating a Simplified Asynchronous Call Pattern for Windows Forms Applications” at http://msdn.microsoft.com/en-us/library/ms996483.aspx
• For more information on the Exception Shielding and Entity Translator patterns, see “Useful Patterns for Services” at http://msdn.microsoft.com/en-us/library/cc304800.aspx

Pattern Descriptions

• Asynchronous Callback. Execute long-running tasks on a separate thread that executes in the background, and provide a function for the thread to call back into when the task is complete.
• Cache Dependency. Use external information to determine the state of data stored in a cache.
• Chain of Responsibility. Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request.
• Composite View . Combine individual views into a composite representation.
• Command Pattern. Encapsulate request processing in a separate command object with a common execution interface.
• Entity Translator. An object that transforms message data types into business types for requests, and reverses the transformation for responses.
• Exception Shielding. Prevent a service from exposing information about its internal implementation when an exception occurs.
• Front Controller . Consolidate request handling by channeling all requests through a single handler object, which can be modified at run time with decorators.
• Model-View-Controller . Separate the UI code into three separate units: Model (data), View (interface), and Presenter (processing logic), with a focus on the View. Two variations on this pattern include Passive View and Supervising Controller, which define how the View interacts with the Model.
• Page Cache. Improve the response time for dynamic Web pages that are accessed frequently but change less often and consume a large amount of system resources to construct.
• Page Controller . Accept input from the request and handle it for a specific page or action on a Web site.
• Passive View . Reduce the view to the absolute minimum by allowing the controller to process user input and maintain the responsibility for updating the view.
• Presentation Model . Move all view logic and state out of the view, and render the view through data-binding and templates.
• Supervising Controller . A variation of the MVC pattern in which the controller handles complex logic, in particular coordinating between views, but the view is responsible for simple view-specific logic.
• Template View . Implement a common template view, and derive or construct views using this template view.
• Transform View . Transform the data passed to the presentation tier into HTML for display in the UI.
• Two-Step View . Transform the model data into a logical presentation without any specific formatting, and then convert that logical presentation to add the actual formatting required.

Technology Considerations

The following guidelines will help you to choose an appropriate implementation technology. The guidelines also contain suggestions for common patterns that are useful for specific types of application and technology.

Mobile Applications

Consider the following guidelines when designing a mobile application:

• If you want to build full-featured connected, occasionally connected, and disconnected executable applications that run on a wide range of Microsoft Windows®–based devices, consider using the Microsoft Windows Compact Framework.
• If you want to build connected applications that require Wireless Application Protocol (WAP), compact HTML (cHTML), or similar rendering formats, consider using ASP.NET Mobile Forms and Mobile Controls.
• If you want to build applications that support rich media and interactivity, consider using Microsoft Silverlight® for Mobile.

Rich Client Applications

Consider the following guidelines when designing a rich client application:

• If you want to build applications with good performance and interactivity, and have design support in Microsoft Visual Studio®, consider using Windows Forms.
• If you want to build applications that fully support rich media and graphics, consider using Windows Presentation Foundation (WPF).
• If you want to build applications that are downloaded from a Web server and then execute on the client, consider using XAML Browser Applications (XBAP).
• If you want to build applications that are predominantly document-based, or are used for reporting, consider designing a Microsoft Office Business Application.
• If you decide to use Windows Forms and you are designing composite interfaces, consider using the Smart Client Software Factory.
• If you decide to use WPF and you are designing composite interfaces, consider using the Composite Application Guidance for WPF.
• If you decide to use WPF, consider using the Presentation Model (Model-View-ViewModel) pattern.
• If you decide to use WPF, consider using WPF Commands to communicate between your View and your Presenter or ViewModel.
• If you decide to use WPF, consider implementing the Presentation Model pattern by using DataTemplates over User Controls to give designers more control.

Rich Internet Applications (RIA)

Consider the following guidelines when designing an RIA:

• If you want to build browser-based, connected applications that have broad cross-platform reach, are highly graphical, and support rich media and presentation features, consider using Silverlight.
• If you decide to use Silverlight, consider using the Presentation Model (Model-View-ViewModel) pattern.

Web Applications

Consider the following guidelines when designing a Web application:

• If you want to build applications that are accessed through a Web browser or specialist user agent, consider using ASP.NET.
• If you want to build applications that provide increased interactivity and background processing, with fewer page reloads, consider using ASP.NET with AJAX.
• If you want to build applications that include islands of rich media content and interactivity, consider using ASP.NET with Silverlight controls.
• If you are using ASP.NET and want to implement a control-centric model with separate controllers and improved testability, consider using the ASP.NET MVC Framework.
• If you are using ASP.NET, consider using master pages to simplify development and implement a consistent UI across all pages.

patterns & practices Solution Assets

• Web Client Software Factory at http://msdn.microsoft.com/en-us/library/bb264518.aspx
• Smart Client Software Factory at http://msdn.microsoft.com/en-us/library/aa480482.aspx
• Composite Application Guidance for WPF at http://msdn.microsoft.com/en-us/library/cc707819.aspx
• Smart Client - Composite UI Application Block at http://msdn.microsoft.com/en-us/library/aa480450.aspx

Additional Resources

• For more information, see Microsoft Inductive User Interface Guidelines at http://msdn.microsoft.com/en-us/library/ms997506.aspx .
• For more information, see User Interface Control Guidelines at http://msdn.microsoft.com/en-us/library/bb158625.aspx .
• For more information, see User Interface Text Guidelines at http://msdn.microsoft.com/en-us/library/bb158574.aspx .
• For more information, see Design and Implementation Guidelines for Web Clients at http://msdn.microsoft.com/en-us/library/ms978631.aspx .
• For more information, see Web Presentation Patterns at http://msdn.microsoft.com/en-us/library/ms998516.aspx .

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Application Architecture Overview

Systems Analysis and Design Tutorial

An application system consists of three logical layers.

The presentation layer is what a system user sees or interacts with.  It can consist of visual objects such as screens, web pages or reports or non-visual objects such as an interactive voice response interface.

When most people think of application systems, they think mainly of the presentation layer.  Unfortunately, this layer represents a small portion of the effort involved in building application systems.

The business logic layer, on the other hand, implements and enforces the business rules via programming logic (computer instructions).

This business logic layer might on the surface appear to be very straight forward, however, that is rarely so.

The data access layer consists of the definitions of database tables and columns and the computer logic that is needed to navigate the database.

The layer in the application architecture enforces rules regarding the storage and access of information. For example: All date fields must be valid dates.  All numeric fields must never contain alphanumeric characters.

This diagram on this page is a "logical" representation of an application system.  When a system is implemented, application system components can be physically deployed on different computer systems.

For example, the presentation of the web page you are looking at is being handled by your computer or mobile device.  The logic required to consolidate and communicate the visual objects that it needs is occurring on a web server located in Virginia USA.

Web Application Architecture: How the Web Works

• Engineering
• Published: 25 Jul, 2019
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What is Web Application Architecture?

• addresses a particular problem, even if it’s simply finding some information
• is as interactive as a desktop application
• has a Content Management System

How does the web request work?

Web request-response cycle

Web application architecture components and Three-Tier Architecture

Web application architecture following the three-tier pattern

Presentation layer

Business layer, persistence layer, example #1. dynamic web pages, spas, and mpas, single page applications.

Single Page Application architecture

Multi-Page Applications

MPA architecture

Example #2. Enterprise applications

Enterprise application architecture

To conclude

• Network infrastructure

presentation layer

• Andrew Froehlich, West Gate Networks

What is the presentation layer?

The presentation layer resides at Layer 6 of the Open Systems Interconnection ( OSI ) communications model and ensures that communications that pass through it are in the appropriate form for the recipient application. In other words, the presentation layer presents the data in a readable format from an application layer perspective.

For example, a presentation layer program could format a file transfer request in binary code to ensure a successful file transfer . Because binary is the most rudimentary of computing languages, it ensures that the receiving device can decipher and translate it into a format the application layer understands and expects.

How the presentation layer works

Once the application layer passes data meant for transport to another device in a certain format, the presentation layer then prepares this data in the most appropriate format the receiving application can understand.

Common data formats include the following:

• American Standard Code for Information Interchange and Extended Binary Coded Decimal Interchange Code for text;
• JPEG , GIF and TIFF for images; and
• MPEG, MIDI and QuickTime for video.

Encryption and decryption of data communications are also performed at the presentation layer. Here, encryption methods and keys exchange between the two communicating devices. Only the sender and receiver can properly encode and decode data so it returns to a readable format.

The presentation layer can serialize -- or translate -- more complex application data objects into a storable and transportable format. This helps to rebuild the object once it arrives at the other side of the communications stream. The presentation layer also deserializes the data stream and places it back into an object format that the application can understand by the application.

The tool that manages Hypertext Transfer Protocol ( HTTP ) is an example of a program that loosely adheres to the presentation layer of OSI.

Although it's technically considered an application-layer protocol per the TCP/IP model , HTTP includes presentation layer services within it. HTTP works when the requesting device forwards user requests passed to the web browser onto a web server elsewhere in the network.

HTTP receives a return message from the web server that includes a Multipurpose Internet Mail Extensions ( MIME ) header. The MIME header indicates the type of file -- text, video, or audio -- that has been received so that an appropriate player utility can present the file to the user.

Functions of the presentation layer

• ensures proper formatting and delivery to and from the application layer;
• performs data encryption; and
• manages serialization of data objects.

Editor's note: This article was republished in January 2023 to improve the reader experience.

Continue Reading About presentation layer

• What is the difference between TCP/IP model vs. OSI model?
• Data and file formatting

Related Terms

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file extension (file format)

network protocol

MIME (Multipurpose Internet Mail Extensions)

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Programming

What is a multi layered software architecture.

Multi layered software architecture is one of the most popular architectural patterns today. It moderates the increasing complexity of modern applications. It also makes it easier to work in a more agile manner. That’s important when you consider the dominance of DevOps and other similar methodologies today. Sometimes called tiered architecture , or n-tier architecture , a multi layered software architecture consists of various layers, each of which corresponds to a different service or integration. Because each layer is separate, making changes to each layer is easier than having to tackle the entire architecture.

Let’s take a look at how a multi layered software architecture works, and what the advantages and disadvantages of it are.

This has been taken from the book Architectural Patterns. Find it here .

What does a layered software architecture consist of?

Before we get into a multi layered architecture, let’s start with the simplest form of layered architecture – three tiered architecture. This is a good place to start because all layered software architecture contains these three elements. These are the foundations:

• Presentation layer : This is the first and topmost layer which is present in the application. This tier provides presentation services, that is presentation, of content to the end user through GUI. This tier can be accessed through any type of client device like desktop, laptop, tablet, mobile, thin client, and so on. For the content to the displayed to the user, the relevant web pages should be fetched by the web browser or other presentation component which is running in the client device. To present the content, it is essential for this tier to interact with the other tiers that are present preceding it.
• Application layer : This is the middle tier of this architecture. This is the tier in which the business logic of the application runs. Business logic is the set of rules that are required for running the application as per the guidelines laid down by the organization. The components of this tier typically run on one or more application servers.
• Data layer : This is the lowest tier of this architecture and is mainly concerned with the storage and retrieval of application data. The application data is typically stored in a database server, file server, or any other device or media that supports data access logic and provides the necessary steps to ensure that only the data is exposed without providing any access to the data storage and retrieval mechanisms. This is done by the data tier by providing an API to the application tier. The provision of this API ensures complete transparency to the data operations which are done in this tier without affecting the application tier. For example, updates or upgrades to the systems in this tier do not affect the application tier of this architecture.

The diagram below shows how a simple layered architecture with 3 tiers works:

These three layers are essential. But other layers can be built on top of them. That’s when we get into multi layered architecture. It’s sometimes called n-tiered architecture because the number of tiers or layers (n) could be anything! It depends on what you need and how much complexity you’re able to handle.

Multi layered software architecture

A multi layered software architecture still has the presentation layer and data layer. It simply splits up and expands the application layer. These additional aspects within the application layer are essentially different services. This means your software should now be more scalable and have extra dimensions of functionality. Of course, the distribution of application code and functions among the various tiers will vary from one architectural design to another, but the concept remains the same.

The diagram below illustrates what a multi layered software architecture looks like. As you can see, it’s a little more complex that a three-tiered architecture, but it does increase scalability quite significantly:

What are the benefits of a layered software architecture?

A layered software architecture has a number of benefits – that’s why it has become such a popular architectural pattern in recent years. Most importantly, tiered segregation allows you to manage and maintain each layer accordingly. In theory it should greatly simplify the way you manage your software infrastructure.

The multi layered approach is particularly good for developing web-scale, production-grade, and cloud-hosted applications very quickly and relatively risk-free. It also makes it easier to update any legacy systems – when you’re architecture is broken up into multiple layers, the changes that need to be made should be simpler and less extensive than they might otherwise have to be.

When should you use a multi layered software architecture?

Clearly, the argument for a multi layered software architecture is pretty clear. However, there are some instances when it is particularly appropriate:

• If you are building a system in which it is possible to split the application logic into smaller components that could be spread across several servers. This could lead to the design of multiple tiers in the application tier.
• If the system under consideration requires faster network communications, high reliability, and great performance, then n-tier has the capability to provide that as this architectural pattern is designed to reduce the overhead which is caused by network traffic.

An example of a multi layered software architecture

We can illustrate the working of an multi layered architecture with the help of an example of a shopping cart web application which is present in all e-commerce sites. The shopping cart web application is used by the e-commerce site user to complete the purchase of items through the e-commerce site.

You’d expect the application to have several features that allow the user to:

• Add selected items to the cart
• Change the quantity of items in their cart
• Make payments

The client tier, which is present in the shopping cart application, interacts with the end user through a GUI. The client tier also interacts with the application that runs in the application servers present in multiple tiers. Since the shopping cart is a web application, the client tier contains the web browser. The presentation tier present in the shopping cart application displays information related to the services like browsing merchandise, buying them, adding them to the shopping cart, and so on. The presentation tier communicates with other tiers by sending results to the client tier and all other tiers which are present in the network.

The presentation tier also makes calls to database stored procedures and web services. All these activities are done with the objective of providing a quick response time to the end user. The presentation tier plays a vital role by acting as a glue which binds the entire shopping cart application together by allowing the functions present in different tiers to communicate with each other and display the outputs to the end user through the web browser.

In this multi layered architecture, the business logic which is required for processing activities like calculation of shipping cost and so on are pulled from the application tier to the presentation tier. The application tier also acts as the integration layer and allows the applications to communicate seamlessly with both the data tier and the presentation tier. The last tier which is the data tier is used to maintain data. This layer typically contains database servers. This layer maintains data independent from the application server and the business logic. This approach provides enhanced scalability and performance to the data tier.

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Three-tier architecture is a well-established software application architecture that organizes applications into three logical and physical computing tiers: the presentation tier, or user interface; the application tier, where data is processed; and the data tier, where application data is stored and managed.

The chief benefit of three-tier architecture is that because each tier runs on its own infrastructure, each tier can be developed simultaneously by a separate development team. And can be updated or scaled as needed without impacting the other tiers.

For decades three-tier architecture was the prevailing architecture for client-server applications. Today, most three-tier applications are targets for modernization that uses cloud-native technologies such as containers and microservices and for migration to the cloud.

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Presentation tier

The presentation tier is the user interface and communication layer of the application, where the end user interacts with the application. Its main purpose is to display information to and collect information from the user. This top-level tier can run on a web browser, as desktop application, or a graphical user interface (GUI), for example. Web presentation tiers are developed by using HTML, CSS, and JavaScript. Desktop applications can be written in various languages depending on the platform.

Application tier

The application tier, also known as the logic tier or middle tier, is the heart of the application. In this tier, information that is collected in the presentation tier is processed - sometimes against other information in the data tier - using business logic, a specific set of business rules. The application tier can also add, delete, or modify data in the data tier. 

The application tier is typically developed by using Python, Java, Perl, PHP or Ruby, and communicates with the data tier by using  API  calls. 

The data tier, sometimes called database tier, data access tier or back-end, is where the information that is processed by the application is stored and managed. This can be a  relational database management system  such as  PostgreSQL , MySQL, MariaDB, Oracle, Db2, Informix or Microsoft SQL Server, or in a  NoSQL  Database server such as Cassandra,  CouchDB , or  MongoDB . 

In a three-tier application, all communication goes through the application tier. The presentation tier and the data tier cannot communicate directly with one another.

Tier versus layer

In discussions of three-tier architecture,  layer  is often used interchangeably – and mistakenly – for  tier , as in 'presentation layer' or 'business logic layer'. 

They aren't the same. A 'layer' refers to a functional division of the software, but a 'tier' refers to a functional division of the software that runs on infrastructure separate from the other divisions. The Contacts app on your phone, for example, is a  three - layer  application, but a  single-tier  application, because all three layers run on your phone.

The difference is important because layers can't offer the same benefits as tiers.

Again, the chief benefit of three-tier architecture is its logical and physical separation of functionality. Each tier can run on a separate operating system and server platform - for example, web server, application server, database server - that best fits its functional requirements. And each tier runs on at least one dedicated server hardware or virtual server, so the services of each tier can be customized and optimized without impacting the other tiers. 

Other benefits (compared to single- or two-tier architecture) include:

• Faster development : Because each tier can be developed simultaneously by different teams, an organization can bring the application to market faster. And programmers can use the latest and best languages and tools for each tier.
• Improved scalability : Any tier can be scaled independently of the others as needed.
• Improved reliability : An outage in one tier is less likely to impact the availability or performance of the other tiers.
• Improved security : Because the presentation tier and data tier can't communicate directly, a well-designed application tier can function as an internal firewall, preventing SQL injections and other malicious exploits.

In web development, the tiers have different names but perform similar functions:

• The web server  is the presentation tier and provides the user interface. This is usually a web page or website, such as an ecommerce site where the user adds products to the shopping cart, adds payment details or creates an account. The content can be static or dynamic, and is developed using HTML, CSS, and JavaScript.
• The application server  corresponds to the middle tier, housing the business logic that is used to process user inputs. To continue the ecommerce example, this is the tier that queries the inventory database to return product availability, or adds details to a customer's profile. This layer often developed using Python, Ruby, or PHP and runs a framework such as Django, Rails, Symphony, or ASP.NET.
• The database server  is the data or backend tier of a web application. It runs on database management software, such as MySQL, Oracle, DB2, or PostgreSQL.

While three-tier architecture is easily the most widely adopted multitier application architecture, there are others that you might encounter in your work or your research.

Two-tier architecture 

Two-tier architecture is the original client-server architecture, consisting of a presentation tier and a data tier; the business logic lives in the presentation tier, the data tier or both. In two-tier architecture the presentation tier - and therefore the end user - has direct access to the data tier, and the business logic is often limited. A simple contact management application, where users can enter and retrieve contact data, is an example of a two-tier application. 

N-tier architecture

N-tier architecture - also called or multitier architecture - refers to  any  application architecture with more than one tier. But applications with more than three layers are rare because extra layers offer few benefits and can make the application slower, harder to manage and more expensive to run. As a result, n-tier architecture and multitier architecture are usually synonyms for three-tier architecture.

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Layered architecture: What it is and how it can help you create applications?

What is web application architecture?

Application architecture is the representation of how different services and systems are joined together. It helps us to understand how applications or services are placed in a layered architecture, who are the different actors at each layer and what is the fundamental role of each layer.

It determines application components and different layers communicate with each other. These architectures are layered having different layers from the design or presentation layer to the data layer. Software architects or Web engineers ensure that all the elements or layers work together correctly.

How does system architecture for web application works?

In web application architecture, there are basically two parts working simultaneously, the client (frontend) and server (backend). The client represents the application UI on the browser from where the web server takes the request to the server, where the server has the code that responds to requests coming from the client. The Server manages the application logic and responds to HTTP requests.

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Models of web architecture

One-tier architecture.

One-tier architecture involves putting all of the required components for a software application or technology on a single server or platform. This kind of architecture is often contrasted with multi-tiered architecture or the three-tier architecture that's used for some Web applications and other technologies where various presentation, business, and data access layers are housed separately.

Two-tier architecture

The Two-tier architecture is divided into two parts: Client Application (Client-side) and Database (Server-side) respectively.

Also called a client-server application, the communication in this architecture takes place between the client (browser) and the server. The client system will send the request to the server system which will process it and send back the data to the client side.

Multiple-tier architecture

A Multi-tier Architecture is a software architecture in which different software components, arranged in tiers (layers), offer dedicated functionality. The most common example of multi-tier architecture is a three-tier system comprising a data management tier (encompassing one or several database servers), a client tier (interface functionality), and an application tier (business logic).

Microservices architecture

You might have heard of the word microservices if you’re a tech enthusiast. Microservices are independent services like applications, which exist completely on their own. These come with their logic, state, and deployment and interact with each other via API calls, queues, etc. depending on the requirements. These microservices combine to deliver the complete application solution.

With microservices architectures, applications are easier to scale and faster to develop allowing businesses to accelerate innovation and time-to-market for new features.

Layers and Components of Application Architecture

The application architecture is made up of several layers: design layer, frontend layer (HTML and CSS), backend or data layer (database and scripting languages), platform (browser/OS), and business layer. These layers are built on top of each other and depend on each other to create a successful project.

Presentation Layer

This layer represents the design and UI components on the client side. Users interact with this layer to send requests through the application layer to the server. It displays the data flow for the users. The main purpose of this layer is to take data from users and show the response from the server (data layer).

Our UI team can help you create the right experience to help your business attract customers’ attention.

Application Layer

The application layer consists of an API gateway. Front-end developers write code to pass the data from the presentation layer to the business logic layer where it is processed. Data will pass to APIs and get stored in the database, depending on the feature it is utilized in the business layer for application logic and to perform certain actions.

Business Layer

This layer has all implementation of application logic. Data from the application layer gets utilized here for example in a lead generation application a form is submitted in the presentation layer and data travels through APIs and is then used to send out emails or to perform any action on the lead before getting stored in the database.

Data or Backend Layer

All the data gets stored in the database and retrieved from it to use on the front end (client-side). Data travels from the database through APIs, from the application layer in creating modules or components that are converted to UI and the user then interacts with that in the presentation layer.

Conclusion :

To conclude, there are different ways to set up the architecture for applications software. Microservices architecture is the most popular choice of mid-sized and large companies like Amazon and Google. However, in order to find out more about which architecture to go with for building your project we recommend you reach out to any professional web development team that can guide you according to your needs and goals.

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What's the difference between "Layers" and "Tiers"?

What's the difference between "Layers" and "Tiers"?

• architecture

• 7 Almost everyone I've met in software world uses these two terms interchangeably as if they are exactly the same. –  RBT Commented Jun 3, 2016 at 9:08
• 2 "Layers refer to the inside of a cake, which can be anywhere between two and six layers of sponge, sandwiched together by buttercream before being decorated. Tiers refer to the number of cakes of increasing size that are stacked on top of each other." Yes, that's a real cooking definition, and pretty enlightening if you compare it to the selected answer: stackoverflow.com/a/120487/7389293 –  carloswm85 Commented Oct 7, 2022 at 19:30

14 Answers 14

Logical layers are merely a way of organizing your code. Typical layers include Presentation, Business and Data – the same as the traditional 3-tier model. But when we’re talking about layers, we’re only talking about logical organization of code. In no way is it implied that these layers might run on different computers or in different processes on a single computer or even in a single process on a single computer. All we are doing is discussing a way of organizing a code into a set of layers defined by specific function. Physical tiers however, are only about where the code runs. Specifically, tiers are places where layers are deployed and where layers run. In other words, tiers are the physical deployment of layers.

Source: Rockford Lhotka, Should all apps be n-tier?

Read Scott Hanselman's post on the issue: A reminder on "Three/Multi Tier/Layer Architecture/Design" :

Remember though, that in "Scott World" (which is hopefully your world also :) ) a "Tier" is a unit of deployment, while a "Layer" is a logical separation of responsibility within code. You may say you have a "3-tier" system, but be running it on one laptop. You may say your have a "3-layer" system, but have only ASP.NET pages that talk to a database. There's power in precision, friends.

Layers refer to the logical separation of code. Logical layers help you organize your code better. For example, an application can have the following layers.

• Presentation Layer or UI Layer
• Business Layer or Business Logic Layer
• Data Access Layer or Data Layer

The above three layers reside in their own projects, maybe 3 projects or even more. When we compile the projects we get the respective layer DLL. So we have 3 DLLs now.

Depending upon how we deploy our application, we may have 1 to 3 tiers. As we now have 3 DLL's, if we deploy all the DLLs on the same machine, then we have only 1 physical tier but 3 logical layers.

If we choose to deploy each DLL on a separate machine, then we have 3 tiers and 3 layers.

So, Layers are a logical separation and Tiers are a physical separation. We can also say that tiers are the physical deployment of layers.

• What i understood from your answer that we can deploy 3 layers(DLL) on three different server. Right ? Can you please tell me how can i give reference of Business Logic layer on presentation layer ? –  Mazhar Khan Commented Jan 9, 2013 at 7:22
• @MazharKhan You might want to use a service to expose the business layer functionality to the presentation layer –  Amit Saxena Commented May 30, 2014 at 1:59

Why always trying to use complex words?

A layer = a part of your code , if your application is a cake, this is a slice.

A tier = a physical machine , a server.

A tier hosts one or more layers.

Example of layers:

• Presentation layer = usually all the code related to the User Interface
• Data Access layer = all the code related to your database access

Your code is hosted on a server = Your code is hosted on a tier.

Your code is hosted on 2 servers = Your code is hosted on 2 tiers.

For example, one machine hosting the Web Site itself (the Presentation layer), another machine more secured hosting all the more security sensitive code (real business code - business layer, database access layer, etc.).

There are so many benefits to implement a layered architecture. This is tricky and properly implementing a layered application takes time. If you have some, have a look at this post from Microsoft: http://msdn.microsoft.com/en-gb/library/ee658109.aspx

I've found a definition that says that Layers are a logical separation and tiers are a physical separation.

In plain english, the Tier refers to "each in a series of rows or levels of a structure placed one above the other" whereas the Layer refers to "a sheet, quantity, or thickness of material, typically one of several, covering a surface or body".

Tier is a physical unit , where the code / process runs. E.g.: client, application server, database server;

Layer is a logical unit , how to organize the code. E.g.: presentation (view), controller, models, repository, data access.

Tiers represent the physical separation of the presentation, business, services, and data functionality of your design across separate computers and systems.

Layers are the logical groupings of the software components that make up the application or service. They help to differentiate between the different kinds of tasks performed by the components, making it easier to create a design that supports reusability of components. Each logical layer contains a number of discrete component types grouped into sublayers, with each sublayer performing a specific type of task.

The two-tier pattern represents a client and a server.

In this scenario, the client and server may exist on the same machine, or may be located on two different machines. Figure below, illustrates a common Web application scenario where the client interacts with a Web server located in the client tier. This tier contains the presentation layer logic and any required business layer logic. The Web application communicates with a separate machine that hosts the database tier, which contains the data layer logic.

Advantages of Layers and Tiers:

Layering helps you to maximize maintainability of the code, optimize the way that the application works when deployed in different ways, and provide a clear delineation between locations where certain technology or design decisions must be made.

Placing your layers on separate physical tiers can help performance by distributing the load across multiple servers. It can also help with security by segregating more sensitive components and layers onto different networks or on the Internet versus an intranet.

A 1-Tier application could be a 3-Layer application.

Layers are logical separation of related-functional[code] within the application and Communication between the layers is explicit and loosely coupled. [ Presentation logic , Application logic , Data Access logic ]

Tiers are Physical separation of layers [which get hosted on Individual servers ] in an individual computer(process).

As shown in diagram:

n- Tier advantages: Better Security Scalability : As your organization grows You can scale up your DB-Tier with DB-Clustering with out touching other tiers. Maintainability : Web designer can change the View-code, with out touching the other layers on the other tiers. Easily Upgrade or Enhance [Ex: You can add Additional Application Code, Upgrade Storage Area, or even add Multiple presentation Layers for Separate devises like mobile, tablet, pc]

I like the below description from Microsoft Application Architecture Guide 2

Layers describe the logical groupings of the functionality and components in an application; whereas tiers describe the physical distribution of the functionality and components on separate servers, computers, networks, or remote locations. Although both layers and tiers use the same set of names (presentation, business, services, and data), remember that only tiers imply a physical separation.

Yes my dear friends said correctly. Layer is a logical partition of application whereas tier is physical partition of system tier partition is depends on layer partition. Just like an application execute on single machine but it follows 3 layered architecture, so we can say that layer architecture could be exist in a tier architecture. In simple term 3 layer architecture can implement in single machine then we can say that its is 1 tier architecture. If we implement each layer on separate machine then its called 3 tier architecture. A layer may also able to run several tier. In layer architecture related component to communicate to each other easily. Just like we follow given below architecture

• presentation layer
• business logic layer
• data access layer

A client could interact to "presentation layer", but they access public component of below layer's (like business logic layer's public component) to "business logic layer" due to security reason. Q * why we use layer architecture ? because if we implement layer architecture then we increase our applications efficiency like

==>security

==>manageability

==>scalability

other need like after developing application we need to change dbms or modify business logic etc. then it is necessary to all.

Q * why we use tier architecture?

because physically implementation of each layer gives a better efficiency ,without layer architecture we can not implement tier architecture. separate machine to implement separate tier and separate tier is implement one or more layer that's why we use it. it uses for the purposes of fault tolerance. ==>easy to maintain.

Simple example

Just like a bank open in a chamber, in which categories the employee:

• gate keeper
• a person for cash
• a person who is responsible to introduce banking scheme

they all are the related components of system.

If we going to bank for loan purpose then first a gate keeper open the door with smile after that we goes to near a person that introduce to all scheme of loan after that we goes to manager cabin and pass the loan. After that finally we goes to cashier's counter take loan. These are layer architecture of bank.

What about tier? A bank's branch open in a town, after that in another town, after that in another but what is the basic requirement of each branch

exactly the same concept of layer and tier.

• Great explanation dear –  Dulaj Kulathunga Commented Jan 21, 2020 at 7:54

I use layers to describe the architect or technology stack within a component of my solutions. I use tiers to logically group those components typically when network or interprocess communication is involved.

Technically a Tier can be a kind of minimum environment required for the code to run.

E.g. hypothetically a 3-tier app can be running on

• 3 physical machines with no OS .

1 physical machine with 3 virtual machines with no OS.

(That was a 3-(hardware)tier app)

1 physical machine with 3 virtual machines with 3 different/same OSes

(That was a 3-(OS)tier app)

1 physical machine with 1 virtual machine with 1 OS but 3 AppServers

(That was a 3-(AppServer)tier app)

1 physical machine with 1 virtual machine with 1 OS with 1 AppServer but 3 DBMS

(That was a 3-(DBMS)tier app)

1 physical machine with 1 virtual machine with 1 OS with 1 AppServers and 1 DBMS but 3 Excel workbooks.

Excel workbook is the minimum required environment for VBA code to run.

Those 3 workbooks can sit on a single physical computer or multiple.

I have noticed that in practice people mean "OS Tier" when they say "Tier" in the app description context.

That is if an app runs on 3 separate OS then its a 3-Tier app.

So a pedantically correct way describing an app would be

"1-to-3-Tier capable, running on 2 Tiers" app.

Layers are just types of code in respect to the functional separation of duties withing the app (e.g. Presentation, Data , Security etc.)

When you talk about presentation, service, data, network layer, you are talking about layers. When you "deploy them separately", you talk about tiers.

Tiers is all about deployment. Take it this way: We have an application which has a frontend created in Angular, it has a backend as MongoDB and a middle layer which interacts between the frontend and the backend. So, when this frontend application, database application, and the middle layer is all deployed separately, we say it's a 3 tier application.

Benefit: If we need to scale our backend in the future, we only need to scale the backend independently and there's no need to scale up the frontend.

Layers are conceptual entities, and are used to separate the functionality of software system from a logical point of view; when you implement the system you organize these layers using different methods; in this condition we refer to them not as layers but as tiers.

IBM's Three-Tier Architecture article has a section dedicated to this topic:

In discussions of three-tier architecture, layer is often used interchangeably – and mistakenly – for tier, as in 'presentation layer' or 'business logic layer.' They aren't the same. A 'layer' refers to a functional division of the software, but a 'tier' refers to a functional division of the software that runs on infrastructure separate from the other divisions. The Contacts app on your phone, for example, is a three-layer application, but a single-tier application, because all three layers run on your phone. The difference is important, because layers can't offer the same benefits as tiers.

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Docker overview

Docker is an open platform for developing, shipping, and running applications. Docker enables you to separate your applications from your infrastructure so you can deliver software quickly. With Docker, you can manage your infrastructure in the same ways you manage your applications. By taking advantage of Docker's methodologies for shipping, testing, and deploying code, you can significantly reduce the delay between writing code and running it in production.

The Docker platform

Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security lets you run many containers simultaneously on a given host. Containers are lightweight and contain everything needed to run the application, so you don't need to rely on what's installed on the host. You can share containers while you work, and be sure that everyone you share with gets the same container that works in the same way.

Docker provides tooling and a platform to manage the lifecycle of your containers:

• Develop your application and its supporting components using containers.
• The container becomes the unit for distributing and testing your application.
• When you're ready, deploy your application into your production environment, as a container or an orchestrated service. This works the same whether your production environment is a local data center, a cloud provider, or a hybrid of the two.

What can I use Docker for?

Fast, consistent delivery of your applications.

Docker streamlines the development lifecycle by allowing developers to work in standardized environments using local containers which provide your applications and services. Containers are great for continuous integration and continuous delivery (CI/CD) workflows.

Consider the following example scenario:

• Your developers write code locally and share their work with their colleagues using Docker containers.
• They use Docker to push their applications into a test environment and run automated and manual tests.
• When developers find bugs, they can fix them in the development environment and redeploy them to the test environment for testing and validation.
• When testing is complete, getting the fix to the customer is as simple as pushing the updated image to the production environment.

Responsive deployment and scaling

Docker's container-based platform allows for highly portable workloads. Docker containers can run on a developer's local laptop, on physical or virtual machines in a data center, on cloud providers, or in a mixture of environments.

Docker's portability and lightweight nature also make it easy to dynamically manage workloads, scaling up or tearing down applications and services as business needs dictate, in near real time.

Running more workloads on the same hardware

Docker is lightweight and fast. It provides a viable, cost-effective alternative to hypervisor-based virtual machines, so you can use more of your server capacity to achieve your business goals. Docker is perfect for high density environments and for small and medium deployments where you need to do more with fewer resources.

Docker architecture

Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which does the heavy lifting of building, running, and distributing your Docker containers. The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon. The Docker client and daemon communicate using a REST API, over UNIX sockets or a network interface. Another Docker client is Docker Compose, that lets you work with applications consisting of a set of containers.

The Docker daemon

The Docker daemon ( dockerd ) listens for Docker API requests and manages Docker objects such as images, containers, networks, and volumes. A daemon can also communicate with other daemons to manage Docker services.

The Docker client

The Docker client ( docker ) is the primary way that many Docker users interact with Docker. When you use commands such as docker run , the client sends these commands to dockerd , which carries them out. The docker command uses the Docker API. The Docker client can communicate with more than one daemon.

Docker Desktop

Docker Desktop is an easy-to-install application for your Mac, Windows or Linux environment that enables you to build and share containerized applications and microservices. Docker Desktop includes the Docker daemon ( dockerd ), the Docker client ( docker ), Docker Compose, Docker Content Trust, Kubernetes, and Credential Helper. For more information, see Docker Desktop .

Docker registries

A Docker registry stores Docker images. Docker Hub is a public registry that anyone can use, and Docker looks for images on Docker Hub by default. You can even run your own private registry.

When you use the docker pull or docker run commands, Docker pulls the required images from your configured registry. When you use the docker push command, Docker pushes your image to your configured registry.

Docker objects

When you use Docker, you are creating and using images, containers, networks, volumes, plugins, and other objects. This section is a brief overview of some of those objects.

An image is a read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization. For example, you may build an image which is based on the ubuntu image, but installs the Apache web server and your application, as well as the configuration details needed to make your application run.

You might create your own images or you might only use those created by others and published in a registry. To build your own image, you create a Dockerfile with a simple syntax for defining the steps needed to create the image and run it. Each instruction in a Dockerfile creates a layer in the image. When you change the Dockerfile and rebuild the image, only those layers which have changed are rebuilt. This is part of what makes images so lightweight, small, and fast, when compared to other virtualization technologies.

A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state.

By default, a container is relatively well isolated from other containers and its host machine. You can control how isolated a container's network, storage, or other underlying subsystems are from other containers or from the host machine.

A container is defined by its image as well as any configuration options you provide to it when you create or start it. When a container is removed, any changes to its state that aren't stored in persistent storage disappear.

Example docker run command

The following command runs an ubuntu container, attaches interactively to your local command-line session, and runs /bin/bash .

When you run this command, the following happens (assuming you are using the default registry configuration):

If you don't have the ubuntu image locally, Docker pulls it from your configured registry, as though you had run docker pull ubuntu manually.

Docker creates a new container, as though you had run a docker container create command manually.

Docker allocates a read-write filesystem to the container, as its final layer. This allows a running container to create or modify files and directories in its local filesystem.

Docker creates a network interface to connect the container to the default network, since you didn't specify any networking options. This includes assigning an IP address to the container. By default, containers can connect to external networks using the host machine's network connection.

Docker starts the container and executes /bin/bash . Because the container is running interactively and attached to your terminal (due to the -i and -t flags), you can provide input using your keyboard while Docker logs the output to your terminal.

When you run exit to terminate the /bin/bash command, the container stops but isn't removed. You can start it again or remove it.

The underlying technology

Docker is written in the Go programming language and takes advantage of several features of the Linux kernel to deliver its functionality. Docker uses a technology called namespaces to provide the isolated workspace called the container. When you run a container, Docker creates a set of namespaces for that container.

These namespaces provide a layer of isolation. Each aspect of a container runs in a separate namespace and its access is limited to that namespace.

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