As the Commerce Server Interchange (CIP) Transport Dictionary passes through the various pipeline stages, the Transport Dictionary's contents, and particularly its business data object, are encoded into the Extensible Markup Language (XML).
The XML standard is a subset of the Standard Generalized Markup Language (SGML), and was developed in 1996 by the SGML Working Group. The reasons for its development, and for its prominence in the CIP, are numerous. For information on the development of this standard by the World Wide Web Consortium, see http://www.w3.org/xml.
First, because XML conforms to the SGML specification, XML data can be transferred over the World-Wide Web, but is not required to conform to the HTML specification. This is a crucial element in its development, because one of the driving objectives behind the development of XML was to diversify the kinds of information that could be transferred and presented over the Web.
Second, XML supports the creation of "self-describing" documents through the use of a document type definition and/or XML data schemas, XML headers in which the creator of a document describes the kinds of information in the document, and the types of resources the document contains.
For purposes of business-to-business commerce, however, the most important feature of XML is that it allows you to define your own document tags, accommodating a great deal of flexibility in the way that business data is described. The baseline requirement for the way business documents are packaged into XML is the minimal provision that the document conform to the expectations of the XML processor, an application designed to interpret the XML data for presentation to the intended recipient.