Any application is accessible to other applications over the Web.
Definition of the UDDI consortium
Web services are self-contained, modular business applications that have open, Internet-oriented, standards-based interfaces.
Definition of the World Wide Web Consortium (W3C)
A Web service is a software system designed to support interoperable machine-to-machine interaction over a network.
It has an interface described in a machine-processable format (specifically WSDL).
Other systems interact with the Web service using SOAP messages.
What is a Web Service?
Web Services are Classes/Methods, NOT Servlets
Loosely-coupled
Encapsulate functionality to logical entities
Reuse of code and functionality
Distributed Architecture
Standardized interface & established Internet protocols
Web Service Interface
Characteristics of a Web Service
A web service interface generally consists of a collection of operations that can be used by a client over the Internet.
The operations in a web service may be provided by a variety of different resources, for example, programs, objects, or databases.
The key characteristic of (most) web services is that they can process XML-formatted SOAP messages. An alternative is the REST approach.
Each web service uses its own service description to deal with the service-specific characteristics of the messages it receives. Commercial examples include Amazon, Yahoo, Google and eBay.
