An initial draft specification XML Protocol Abstract Model has been published by the W3C XML Protocol Working Group. The draft document has been developed "in order to provide a useful framework for the evaluation of candidate protocols and for reasoning about the development of the protocol itself." According to the WD, "the challenge of crafting a protocol specification is to create a description of behaviour that is not tied to any particular approach to implementation. There is a need to abstract away from some of the messy implementation details of buffer management, data representation and specific APIs. However, in order to describe the behaviour of a protocol one has to establish a set of (useful) concepts that can be used in that description. An abstract model is one way to establish a consistent set of concepts. An abstract model is a tool for the description of complex behaviour -- it is not a template for an implementation... although it should not stray so far away from reality that it is impossible to recognise how the required behaviours would be implemented... As the XML Protocol Working Group labored on the XML Protocol Requirements document and the emerging specification, they also set out to describe how such a technology might ultimately be designed at an abstract level. The resulting Working Draft, the XML Protocol Abstract Model, also provides a shared vocabulary for both members of the Working Group, and other developers already at work on applications that make use of earlier versions of SOAP."

Section 2 of the working draft presents an overview of the abstract model; Section 3 presents a model for the services provided by the XML protocol layer to XML protocol applications; Section 4 presents a model for the extensible processing of XML protocol messages; Section 5 presents a model for the binding of XML protocol to underlying protocol layers.

From the announcment: "Data transport is as central to modern computing as is data storage and display in the networked, decentralized, and distributed environment that is the Web. As XML emerges as the preferred format for data processing, the challenge is for both the sender and the receiver to agree on a transfer protocol at the application level or layer - whether the transfer is to occur between software programs, machines, or organizations. W3C's XML Protocol Activity addresses this problem, and has been at work on both requirements for an XML Protocol specification and on the specification itself, using the W3C Note SOAP/1.1 as a model for evaluation. After producing the XML Protocol Requirements document and reviewing significant feedback from developer communities, the XML Protocol Working Group has published SOAP Version 1.2 and the XML Protocol Abstract Model."