Web application

An application delivered to end users via the World Wide Web. Web applications are popular due to the ubiquity of the web browser as an application client, and also because they can be updated without requiring a redistribution of software (e.g., the company producing the application does not have to redistribute a CD ROM).

Though many variations are possible, a web application is commonly structured as a three-tiered application. In its most common form, a web browser is the first tier, an engine created using some dynamic web content technology (e.g., CGI, PHP, or Java servlets) is the middle tier, and a database is the third tier. The web browser sends requests to the middle tier, which services them by making queries and updates against the database and generating a user interface.

An emerging strategy for application software companies is to provide web-accessible access to software that has heretofore been distributed as local applications. These programs allow the user to pay a monthly or yearly fee for use of a software application without having to install it on a local hard drive. A companies which follows this strategy is known as an application service provider (ASP), and ASPs are currently receiving much attention in the software industry.