Web services is
a standardized way or medium to propagate communication between the client and server applications on the World Wide Web.
Web services provide
- a common platform that allows multiple applications built on various programming languages to have the
- ability to communicate with each other
Popular Web Services Protocols are:
- SOAP = Simple Object Access Protocol
- WSDL = Web Services Description Language
- REST = REpresentational State Transfer
- developed as an intermediate language so that applications built on various programming languages could talk quickly to each other and avoid the extreme development effort.
- Simple Object Access Protocol
- Web Services Description Language
- WSDL is an XML-based file which tells the client application what the web service does and gives all the information required to connect to the web service.
- stands for REpresentational State Transfer.
- REST is used to build Web services that are lightweight, maintainable, and scalable.
A web service is a software module which is designed to perform a certain set of task:
- can be searched for over the network and can also be invoked accordingly
- When invoked the web service would be able to provide functionality to the client which invokes that web service.
- The client would invoke a series of web service calls via requests to a server which would host the actual web service.
- These requests are made through what is known as remote procedure calls. Remote Procedure Calls(RPC) are calls made to methods which are hosted
- by the relevant web service.
The main component of a web service
- is the data which is transferred between the client and the server, and that is XML. XML (Extensible markup language) is a counterpart to HTML and easy to understand the intermediate language that is understood by many programming languages.
- So when applications talk to each other, they actually talk in XML. This provides a common platform for application developed in various
- programming languages to talk to each other.
- Web services use something known as SOAP (Simple Object Access Protocol) for sending the
- XML data between applications. The data is sent over normal HTTP. The data which is sent from the web service to the application is called a SOAP message. The SOAP message is nothing but an XML document.
Web Services Advantages
- Exposing Business Functionality on the network
- Interoperability amongst applications
- A Standardized Protocol which everybody understands
- Reduction in cost of communication - over http
Web service Characteristics
- XML-Based: uses XML to represent the data at the representation and data transportation layers. Using XML eliminates any networking, operating system, or platform sort of dependency
- Loosely Coupled: Loosely coupled means that the client and the web service are not bound to each other, which means that even if the web service changes over time, it should not change the way the client calls the web service.
- Synchronous or Asynchronous functionality: In synchronous operations, the client will actually wait for the web service to complete an operation.
- RPCs: Ability to support Remote Procedure Calls
- Supports Document Exchange:
SOAP was designed to
work with XML over HTTP and have some sort of specification which could be used across all applications.
W3C consortium which is the governing body for all web standards.