web service:-
A web service is
Language Independent.
Protocol Independent.
Platform Independent.
It assumes a stateless service architecture.
Scalable (e.g. multiplying two numbers together to an entire customer-relationship management system).
Programmable (encapsulates a task).
Based on XML (open, text-based standard).
Self-describing (metadata for access and use).
Discoverable (search and locate in registries)- ability of applications and developers to search for and locate desired Web services through registries. This is based on UDDI.
Key Web Service Technologies
XML- Describes only data. So, any application that understands XML-regardless of the application's programming language or platform-has the ability to format XML in a variety of ways (well-formed or valid).
SOAP- Provides a communication mechanism between services and applications.
WSDL- Offers a uniform method of describing web services to other programs.
UDDI- Enables the creation of searchable Web services registries.