In software engineering, multi-tier architecture (often referred to as n-tier architecture) is a client-server architecture in which an application is executed by more than one distinct software agent. For example, an application that uses middleware to service data requests between a user and a database employs multi-tier architecture. The most widespread use of "multi-tier architecture" refers to three-tier architecture. The Three-tier system of alcohol distribution is the system for distributing alcoholic beverages set up in the United States after the repeal of Prohibition. ... Software engineering (SE) is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... This article is about integration software. ... This article is about computing. ...

Three-tier architecture

Visual overview of a Three-tiered application

'Three-tier'^[1] is a client-server architecture in which the user interface, functional process logic ("business rules"), computer data storage and data access are developed and maintained as independent modules, most often on separate platforms. Image File history File links Overview_of_a_three-tier_application. ... Image File history File links Overview_of_a_three-tier_application. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... The user interface is the part of a system exposed to users. ... Business Logic is a non-technical term generally used to describe the functional algorithms which handle information exchange between a database and a user interface. ... 1 GiB of SDRAM mounted in a personal computer. ... Data Access typically refers to software and activities related to storing, retrieving, or acting on data housed in a database or other repository. ... A module is a software entity that groups a set of (typically cohesive) subprograms and data structures. ... In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. ...

The three-tier model is considered to be a software architecture and a software design pattern. The software architecture of a program or computing system is the structure or structures of the system, which comprise software components, the externally visible properties of those components, and the relationships between them. ... In software engineering, design patterns are standard solutions to common problems in software design. ...

Apart from the usual advantages of modular software with well defined interfaces, the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently as requirements or technology change. For example, a change of operating system from Microsoft Windows to Unix would only affect the user interface code. Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... By the mid 20th century humans had achieved a mastery of technology sufficient to leave the surface of the Earth for the first time and explore space. ... An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ... Windows redirects here. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ...

Typically, the user interface runs on a desktop PC or workstation and uses a standard graphical user interface, functional process logic may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe contains the computer data storage logic. The middle tier may be multi-tiered itself (in which case the overall architecture is called an "n-tier architecture"). A stylised illustration of a personal computer A personal computer (PC) is a computer whose original sales price, size, and capabilities make it useful for individuals, intended to be operated directly by an end user, with no intervening computer operator. ... SGI O2 Workstation To meet Wikipedias quality standards, this article or section may require cleanup. ... GUI redirects here. ... An application server is a software engine that delivers applications to client computers or devices, typically through the internet and using the http protocol. ... A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by Edgar F. Codd. ... A database server is a computer program that provides database services to other computer programs or computers, as defined by the client-server model; the term may also refer to a computer dedicated to running such a program. ... For other uses, see Mainframe. ...

The 3-Tier architecture has the following three tiers:

Presentation Tier

This is the top most level of the application. The presentation tier displays information related to such services as browsing merchandise, purchasing, and shopping cart contents. It communicates with other tiers by outputting results to the browser/client tier and all other tiers in the network.

Application Tier (Business Logic/Logic Tier)

The logic tier is pulled out from the presentation tier and, as its own layer, it controls an application’s functionality by performing detailed processing.

Data Tier

This tier consists of Database Servers. Here information is stored and retrieved. This tier keeps data neutral and independent from application servers or business logic. Giving data its own tier also improves scalability and performance.

Business Logic is a non-technical term generally used to describe the functional algorithms which handle information exchange between a database and a user interface. ...

Comparison with the MVC architecture

At first glance the three tiers may seem similar to the Model-view-controller (MVC) concept, however topologically they are different. A fundamental rule in a three-tier architecture is the client tier never communicates directly with the data tier; in a three-tier model all communication must pass through the middleware tier. Conceptually the three-tier architecture is linear. However, the MVC architecture is triangular: the View sends updates to the Controller, the Controller updates the Model, and the View gets updated directly from the Model. This article or section should include material from Model view controller triad Model-View-Controller (MVC) is a software architecture that separates an applications data model, user interface, and control logic into three distinct components so that modifications to the view component can be made with minimal impact to...

From a historical perspective the three-tier architecture concept emerged in the 1990's from observations of distributed systems (e.g., web applications) where the client, middleware and data tiers ran on physically separate platforms. Whereas MVC comes from the previous decade (by work at Xerox PARC in the late 1970's and early 1980's) and is based on observations of applications that ran on a single graphical workstation; MVC was applied to distributed applications much later in its history (see Model 2). Bold text // Headline text Link title This article is about the computer research center. ... In the design of Java Web applications, there are generally used two design models called Model 1 and Model 2. ...

Web Development usage

In the Web development field, three-tier is often used to refer to Websites, commonly Electronic commerce websites, which are built using three tiers: Web development is a broad term for any activities related to developing a web site for the World Wide Web or an intranet. ... A website (alternatively, Web site or web site) is a collection of Web pages, images, videos or other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet, cell phone or a LAN. A Web page is a document, typically written in HTML... Electronic commerce, commonly known as e-commerce or eCommerce, consists of the buying and selling of products or services over electronic systems such as the Internet and other computer networks. ...

1. A front end Web server serving static content.
2. A middle dynamic content processing and generation level Application server, for example Java EE platform.
3. A back end Database, comprising both data sets and the Database management system or RDBMS software that manages and provides access to the data.

The inside/front of a Dell PowerEdge web server The term Web server can mean one of two things: A computer program that is responsible for accepting HTTP requests from clients, which are known as Web browsers, and serving them HTTP responses along with optional data contents, which usually are... An application server is a software engine that delivers applications to client computers or devices, typically through the internet and using the http protocol. ... Java 2 Platform, Enterprise Edition or Java EE (formerly also J2EE) is a programming platform — part of the Java platform — for developing and running distributed multi-tier architecture applications, based largely on modular components running on an application server. ... This article is about computing. ... A database management system (DBMS) is computer software designed for the purpose of managing databases. ... A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by Edgar F. Codd. ...

Other Considerations

The data transfer methods between the 3 tiers must also be considered. The data exchange may be file-based, client-server, event-based, etc. Protocols involved may include one or more of SNMP, CORBA, Java RMI, .NET Remoting, Sockets, UDP, or other proprietary combinations/permutations of the above types and others. Typically a single "middle-ware" implementation of a single protocol is chosen as the "standard" within a given system, such as J2EE (which is Java specific) or CORBA (which is language/OS neutral). Which protocol is chosen affects such issues as the ability to include legacy applications/libraries, performance, maintainability, etc. When choosing a "middle-ware protocol" (not to be confused with the "middle-of-the-three-tiers"), engineers should not be swayed by public opinion about a protocol's modernness, but should consider the technical benefits and suitability given the problem at hand. For example CGI is very old and "out of date" but is still quite useful and powerful, so is shell scripting, and UDP for that matter. The Simple Network Management Protocol (SNMP) forms part of the internet protocol suite as defined by the Internet Engineering Task Force. ... In computing, Common Object Request Broker Architecture (CORBA) is a standard for software componentry, created and controlled by the Object Management Group (OMG). ... The Java Remote Method Invocation API, or RMI, is a Java application programming interface for performing remote procedural calls. ... . ... It has been suggested that Socket be merged into this article or section. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... Java 2 Platform, Enterprise Edition or J2EE is a Standard (albeit with no ISO or ECMA standard) for developing distributed Multi-tier architecture applications, based on modular components running on an application server. ... In computing, Common Object Request Broker Architecture (CORBA) is a standard for software componentry, created and controlled by the Object Management Group (OMG). ...

Ideally the high-level system abstract design is based on business rules and not on the front-end/back-end technologies. The tiers should be populated with functionality in such a way as to minimize dependencies, and isolate functionalities in a coherent manner - knowing that everything is likely to change, and changes should be made in the fewest number of places, and be testable.

See also

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. This article does not cite any references or sources. ... “GFDL” redirects here. ...

• Business logic
• Client-server architecture
• Database-centric architecture
• Front-end and back-end
• Model-view-controller (MVC)
• Rich Internet application
• SAP R/3 is a client/server based application, utilizing a 3-tiered model.
• Web application

Business Logic is a non-technical term generally used to describe the functional algorithms which handle information exchange between a database and a user interface. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... Database-centric architecture is a term that has several distinct meanings, all of which relate to software architectures in which databases play a crucial role. ... In their most general meanings, the terms front-end and back-end refer to the initial and the end stages of a process flow. ... This article or section should include material from Model view controller triad Model-View-Controller (MVC) is a software architecture that separates an applications data model, user interface, and control logic into three distinct components so that modifications to the view component can be made with minimal impact to... For the geographical term, see ria. ... SAP R/3 is the former name of the main enterprise resource planning software produced by SAP AG. Its new name is SAP ERP. // The first version of SAPs flagship enterprise software was a financial Accounting system named R/1. ... In software engineering, a web application is an application delivered to users from a web server over a network such as the World Wide Web or an intranet. ...

External links

• Linux journal, Three Tier Architecture

References

1. ^ Eckerson, Wayne W. "Three Tier Client/Server Architecture: Achieving Scalability, Performance, and Efficiency in Client Server Applications." Open Information Systems 10, 1 (January 1995): 3(20)

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