Web services are application services , typically combining data and procedural aspects, that are made available over a network such as the internet or an intranet. These services are described in terms of application programming interfaces (API) or web APIs that can be accessed over a network and executed on a remote system hosting the requested services.
An exhaustive description of web services is beyond the scope of this document. Indeed, often web services is a term that includes formal W3C specifications such as SOAP along with less formal, but well described, services such as REST, and even rich internet application (RIA) technologies such as AJAX. Our focus will be on the more formal web services, SOAP and REST, with a brief consideration of RIA techniques.