application server

1. A first-tier, front-end, Web browser-based graphical user interface, usually at a personal computer or workstation
2. A middle-tier business logic application or set of applications, possibly on a local area network or intranet server
3. A third-tier, back-end, database and transaction server, sometimes on a mainframe or large server

Older, legacy application databases and transaction management applications are part of the back end or third tier. The application server is the middleman between browser-based front-ends and back-end databases and legacy systems.

In many usages, the application server combines or works with a Web (Hypertext Transfer Protocol) server and is called a Web application server. The Web browser supports an easy-to-create HTML-based front-end for the user. The Web server provides several different ways to forward a request to an application server and to forward back a modified or new Web page to the user. These approaches include the Common Gateway Interface (CGI), FastCGI, Microsoft's Active Server Page, and the Java Server Page. In some cases, the Web application servers also support request "brokering" interfaces such as CORBA Internet Inter-ORB Protocol (IIOP).

Read more about application server: - TechMetrix Research maintains an Application Server Directory . - Dynalivery Corporation markets a report formatting server that works with several different Web application servers. They describe a version of the three-tier application model . - IBM's WebSphere Application Server is part of its Enterprise Java Beans (EJB) environment. - DCI , developers of information technology seminars, includes the idea of application servers in its Enterprise Architecture and other seminars. - SearchWin2000.com has a collection of Internet links related to application servers.

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