What is Webservice?
Web services are server side programs that listen for messages from client applications and return specific information. This information may come from web service itself, from other componemts in the same domain, or from other web services.
A web service is a collection of protocols and standards used for exchanging data between applications or systems. Web services provide a standard means of communication among different software applications, running on a variety of platforms and/or frameworks. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards. So it is hetrogeneous.
The World Wide Web is more and more used for application to application communication. The programmatic interfaces made available are referred to as Web services.
There are numerous definitions of Web services, which has led to some confusion among IT executives. Loosely defined, Web services allow enterprises to knit together various business information and applications, both in-house and with outside partners, by using standards for integration such as XML, SOAP, and UDDI. Web services are considered a relatively inexpensive way to derive more value from previous IT investments by improving workflow and business efficiency - a major draw in the current economic climate.
W3C Definition
Definition: A Web service is a software system identified by a URI, whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by internet protocols
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Basic Web services architecture components are typically defined using XML applications, use XML infoset definitions for message data typing and structuring, and use HTTP for transport. Extended Web services architecture components are typically defined using extensions to the core XML applications and transports, including alternatives to HTTP.
A message is defined as a construct that can include zero or more headers in addition to data. The header part of a message can include information pertinent to extended Web services functionality, such as security, transaction context, orchestration information, or message routing information. The data part of a message contains the message content or data.
A web service is described using a standard, formal XML notion, called its service description, that provides all of the details necessary to interact with the service, including message formats (that detail the operations), transport protocols, and location. The nature of the interface hides the implementation details of the service so that it can be used independently of the hardware or software platform on which it is implemented and independently of the programming language in which it is written.
Web services can be used alone or in conjunction with other web services to carry out a complex aggregation or a business transaction.