About Web Services

A web service is a program that can be accessed remotely using different standards-based languages. What this program can do (that is, the functionality it implements) is described in a standard vocabulary.

Major benefits of web services include:

Interoperability among distributed applications that span diverse hardware and software platforms
Easy, widespread access to applications through firewalls using web protocols
A cross-platform, cross-language data model (XML) that facilitates developing heterogeneous distributed applications

Web services are characterized by three factors:

What they do (the business functionality they expose)
Where they are (the web site which exposes that functionality)
How they can be accessed (the set of published interfaces necessary to use the exposed functionality)

Web services rely on XML-based and other industry standards:

Extensible Markup Language (XML): A data format that allows uniform communication between web services consumers and web services providers.
XML Schema: A framework that describes XML vocabularies used in business transactions.
Simple Object Access Protocol (SOAP): A protocol for exchanging structured information in the implementation of web services.
Web Services Description Language (WSDL): An XML-based language providing a model for describing SOAP-based web services.
WS-Policy: The WS-Policy framework provides a flexible and extensible grammar for describing the capabilities, requirements, and general characteristics of web services using policies.

In summary, web services are loosely coupled, distributed environments that allow companies to integrate heterogeneous applications within the enterprise or expose business functions to their customers and partners over the Internet. Because you access web services using standard web protocols such as XML and HTTP, the diverse and heterogeneous applications on the web (which typically already understand XML and HTTP) can automatically access web services and communicate with each other.