Web service

Representational State Transfer (REST) is an architecture for well-behaved Web services that can function at Internet scale.

[2] Restful APIs do not require XML-based Web service protocols (SOAP and WSDL) to support their interfaces.

Other systems interact with the web service in a manner prescribed by its description using SOAP-messages, typically conveyed using HTTP with an XML serialization in conjunction with other web-related standards.W3C Web Services may use SOAP over HTTP protocol, allowing less costly (more efficient) interactions over the Internet than via proprietary solutions like EDI/B2B.

Besides SOAP over HTTP, Web services can also be implemented on other reliable transport mechanisms like FTP.

It is a software function provided at a network address over the Web with the service always-on as in the concept of utility computing.

[a]) A directory called UDDI (Universal Description, Discovery, and Integration) defines which software system should be contacted for which type of data.

Critics of non-RESTful Web services often complain that they are too complex[8] and based upon large software vendors or integrators, rather than typical open source implementations.

There are also concerns about performance due to Web services' use of XML as a message format and SOAP/HTTP in enveloping and transporting.

[14][15] A key study published in WWW2008 Conference (Beijing, China)[16] presented the state of SOAP-based web services and concluded that only 63% of the available SOAP-based web services at the time of the study were actually active or can be invoked.