Acronym for Simple Object Access Protocol.

It's a way for a computer program to call a function on another computer, a concept known as RPC. Previously known RPC implementations have always been somewhat platform and/or language specific. SOAP's answer is to use XML for Serialisation in marshalling the call and HTTP to transport it. In other words: SOAP is a bloated, over engineered implementation of a perfectly trivial concept. Sigh.

The canonical SOAP service is a WebServer at IBM which returns (delayed) stock quotes.

This Wiki has a SOAP source letting you grab the wiki source of a webpage. There's a WSDL file describing this source, and you can use xmethods.net to get a human readable version of it.

See also AXIS.