SOAP Version 1.2 (SOAP) is a lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It uses XML technologies to define an extensible messaging framework providing a message construct that can be exchanged over a variety of underlying protocols. The framework has been designed to be independent of any particular programming model and other implementation specific semantics.

ISO/IEC 40210:2011 defines the SOAP messaging framework consisting of:

• the SOAP processing model defining the rules for processing a SOAP message;
• the SOAP Extensibility model defining the concepts of SOAP features and SOAP modules;
• the SOAP underlying protocol binding framework describing the rules for defining a binding to an underlying protocol that can be used for exchanging SOAP messages between SOAP nodes;
• the SOAP message construct defining the structure of a SOAP message.