Defining Characteristics of Web Services
A Web service exhibits the following defining characteristics:
A Web service is a Web resource. You access a Web service using platform-independent and language-neutral Web protocols, such as HTTP. These Web protocols ensure easy integration of heterogeneous environments.
A Web service provides an interface—a Web API—that can be called from another program. This application-to-application programming interface can be invoked from any type of application. The Web API provides access to the application logic that implements the service.
A Web service is typically registered and can be located through a Web service registry. A registry enables service consumers to find services that match their needs. These service consumers may be humans or other applications.
Web services support loosely coupled connections between systems. Web services communicate by passing XML messages to each other via a Web API, which adds a layer of abstraction to the environment that makes the connections flexible and adaptable.