In Simple Term, Web Services are an independent software system designed for interoperability between machine to machine over the network. Web Services open up a way to expose the functionality of an information system and make it available through standard Web technologies(HTTP or HTTPS). It also reduces heterogeneity due to standard web technologies use and is, therefore, key to facilitating application integration. Furthermore, we show that Web services naturally enable new computing paradigms and architectures, and are specifically geared toward service-oriented computing, a paradigm often touted in the past but never quite realized.
The definition is written before seems complete but let’s see the definition by the UDDI consortium
Web services are “self-contained, modular business applications that have open, Internet-oriented, standards-based interfaces.
The above definition is more detailed, placing the emphasis on the need for being compliant with Internet standards. In addition, it requires the service to be open, which essentially means that it has a published interface that can be invoked across the Internet. In spite of this clarification, the definition is still not precise enough. For instance, it is not clear what is meant by a modular, self-contained business application.
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