Several folks in the computing industry think of 1999 as having been the "Year of the Application Server." But while the term application server itself may be a fairly recent addition to the software computing vocabulary, the application server market has already become one of the fastest-growing markets in n-tier computing. Business analysts estimate its value as being likely to reach the multibillion-dollar level in 2001.
In today's distributed computing environment, the term application server is associated with state-of-the-art technology. Perhaps that's why several vendors sell their products under the category of application servers, regardless of whether the product actually offers the features of a basic application server or not. For example, there are site builders, Web page designers, integrated development environments, Web development tools and enterprise-level development environments. The definition of what comprises an application server is more often than not open for interpretation.
What's an Application Server?
An application server is, by definition, "a computer server that serves applications." More precisely, an application server serves up application services. The main purpose of an application server is to reduce the workload of applications by taking over the responsibility of mundane activities involved in executing the application and making the application's services available to external modules in a reliable manner.
I'd like to take a stab at defining an application server as follows: an application server is a computer program that resides on a server in a distributed network and whose main function is to provide the business logic for an application program; an application server provides a customizable and flexible execution environment for hosting business logic components, thus providing distributed services and integrity for application execution.
Traditionally, the application server has been associated with three-tier applications. To recap, the components of a three-tier application are:
- Front-end client: Typically a graphical user interface on a personal computer, laptop or a workstation
- Middle-tier application: Typically a business logic application on a LAN or the intranet server
- Back-end application: Typically a database/transaction server that provides access to legacy or back-office data
Benefits of Application Servers
The Internet being the most powerful phenomenon driving application development and deployment today, application servers came into existence because of a need in the market to offer flexible, robust, extensible and standards-based enterprise applications that are developed at Internet speeds.
