Web Application vs Web Services
A web application uses Web technologies to provide functionality to an end user. A web service uses Web technologies to provide functionality to another software application.
Web services are open standard based Web applications that interact with other web applications for the purpose of exchanging data.
XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, and then waits for a corresponding XML response. Because all communication is in XML, web services are platform neutral and language neutral. Java can talk with Perl;
Windows applications can talk with UNIX applications. Web services conceptually are just specialized web applications:
Body of web services request and response will be SOAP message which defines a protocol for message exchange between applications.
Popular examples for Web Services
1. Currency Converter
2. Temperature conversion
3. Weather Forecast system
4. Credit card validation system
Standard web services technologies:
Higher-level API’s such as JAX-RPC and others are often used to automatically generate web services client and server communication software. Microsoft .NET framework is one popular alternative to JAX-RPC