Apache SOAP 2.2 Overview Page 2

Using XML in SOAP

SOAP messages are structured using XML. Within the framework of the remote procedure call (RPC), it represents the parameters of the methods, the return values, and any potential error messages linked to the processes.

Coding SOAP messages in XML enables universal communication between applications, services, and platforms via the Internet. To do this, SOAP makes use of the descriptive nature of the XML language, thus transforming the content into an application.

In more technical terms, just as with an XML fragment, SOAP messages make references to different namespaces, enabling the content to be validated. They must therefore include a call to SOAP namespaces, making it possible to define and specify the use of standard tags in the message and to ensure compatibility between SOAP versions. As soon as a SOAP message is received, the SOAP tags are validated, as are the tags that express the subject of the message. If it fails, an error is generated.

SOAP thus defines two namespaces:

• http://schemas.xmlsoap.org/soap/envelope/ for the envelope
• http://schemas.xmlsoap.org/soap/encoding/ for the coding