How To Define Application Server

Business enterprises often set up their computer networks in what is called multi-tier architecture. This is still a type of client-server architecture where one or several high-performance machines function as servers and individual users in the network use client computers. The distinct characteristic of a multi-tier architecture is in the way it is set up. There are usually three levels: the presentation tier, the logic tier, and the data tier. This structure is also known as a software framework ('servers' can refer to both hardware and computer application). The presentation tier is the top level of this framework which deals with user interface; this is the client side of the network. The databases and file systems compose the data tier, the bottom level. Between these two, the logic tier facilitates access, coordination and evaluation of requests and responses. This facilitating process is also sometimes known as business logic - the rules that define the exchange of information. This framework is modular; meaning any of the three levels can be replaced or upgraded independently of the others. For example the operating system at the presentation tier could be replaced and this would only entail changing the codes for user interface, leaving all the other levels operating as usual.

The application server plays a significant role in this framework. It centralizes the necessary computer applications for all the users/members of the organization. This is known as application hosting. Instead of installing every type of software in every individual user's computer, the software applications are located in one or a few servers accessible by all users. Distribution, access and configurations for usage are handled by deployment servers. The advantage is that updates and upgrades are guaranteed for all users. All members of the business enterprise are using the same version, no compatibility issues will occur and thus the work flows smoothly. The performance of the applications is also improved despite heavy usage because application servers can manage network traffic and localize it on the presentation tier. Since access to the database and file systems are controlled and are managed from one point (logic tier), security is also enhanced.

Because multi-tier architecture is modular, interoperability is a key factor. How can several users with varying operating systems, using various applications work together? Application servers make this possible through middleware or a middleware server. The term refers to any set of applications (possibly located in specific hardware or several machines) which allow multiple processes to interact. It connects two or more different applications and facilitates the exchange of data between them. Different applications can access one central database because of a middleware server. Middleware plays a central role in logic tier of the architecture.