Discuss the structure of distributed applications.

What will be an ideal response?

The Internet makes it possible for both people and Web applications to communicate and share information with each other. Many Web applications also take advantage of the Internet's connectivity to access Web services to provide specialized information or content. Three-tiered architecture includes a presentation tier, which is responsible for all aspects of displaying information to the user. The presentation tier communicates with the middle tier, which performs the application's logic and obtains data from a database tier.

A distributed application architecture, sometimes called multi-tiered application architecture, adds a services tier to the three-tiered architecture diagram, so that servers running Web applications may invoke Web services running on remote servers over the Internet automatically.

In distributed application architecture, the presentation tier continues to handle the display of information to the user. The middle tier, or business logic tier, handles the interchange of information, and the database tier provides data from associated databases. The services tier represents Web services residing in the Cloud that an application may access over the Internet. In a distributed application architecture, a Web application and its processing are often distributed among many different devices and servers all connected by the Internet.

An application that makes use of Web services is said to have a service-oriented architecture (SOA). An advantage of using Web services to build complex applications is that the applications calling Web services do not need to know anything about how the services work. They just need to know what information each service requires as input and in what format the results will be returned as output. This approach allows the applications to concentrate on their core business logic without having to create or manage content that can be obtained from third-party providers.