WebService

Web Service is a collection of protocols and standards used for exchanging data between applications

Three types of Web Services

1) XML-RPC (Remote Procedure Call)
2) SOAP (Simple Object Access Protocol)
3) REST (Representative State Transfer)

XML-RPC

XML-RPC is a simple, portable way to make remote procedure calls over HTTP


SOAP

"Simple Object Access Protocol" was designed to be a platform and language-neutral alternative to previous middleware techologies like CORBA and DCOM.

REST

RESTful web services, the emphasis is on simple point-to-point communication over HTTP using plain old XML (POX).


SOAP

As communications protocols and message formats are standardized in the web community, it becomes increasingly possible and important to be able to describe the communications in some structured way. WSDL addresses this need by defining an XML grammar for describing network services as collections of communication endpoints capable of exchanging messages. WSDL service definitions provide documentation for distributed systems and serve as a recipe for automating the details involved in applications communication.

A WSDL document defines services as collections of network endpoints, or ports. In WSDL, the abstract definition of endpoints and messages is separated from their concrete network deployment or data format bindings. This allows the reuse of abstract definitions:messages, which are abstract descriptions of the data being exchanged, and port types which are abstract collections ofoperations. The concrete protocol and data format specifications for a particular port type constitutes a reusable binding. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Hence, a WSDL document uses the following elements in the definition of network services:

• Types– a container for data type definitions using some type system (such as XSD).
• Message– an abstract, typed definition of the data being communicated.
• Operation– an abstract description of an action supported by the service.
• Port Type–an abstract set of operations supported by one or more endpoints.
• Binding– a concrete protocol and data format specification for a particular port type.
• Port– a single endpoint defined as a combination of a binding and a network address.
• Service– a collection of related endpoints.