Durable Definition of Scope

In the spirit of not "deriv[ing] properties from certain existing
technologies or interactions and project[ing] them as intrinsic
properties of web services", let me propose the attached figure and the
following verbiage to the editors:

Web services are basically applications that communicate with other
applications over the Web via well defined interfaces and
standards-based Web messaging protocols.  The communication mechanism is
most commonly XML, more specifically in the form of a SOAP (Simple
Object Access Protocol) header, which is the envelop for the message,
and a SOAP body which contains the message itself in XML form.  This
SOAP message is usually transmitted over HTTP, although other transport
mechanisms are possible.  The description of the Web service interface
is most commonly expressed in XML via WSDL (Web Services Description
Language).
 
Although the brief description above is the most common form for Web
services, there are in fact a number of possible technology stacks that
can be used to make Web services.  Figure X shows some of these
possibilities.  The technology stack labelled SOA (Service Oriented
Architecture) Web services represents the current norm and will be the
basis for the more detailed aspects of this reference architecture.  The
other alternative stacks, however, are also consistent with the high
level architecture of Web services.  In this figure WS-RM refers to that
which will presumably shake out of WS-Relibility, WS-ReliableMessaging
and whatever else is in play. Similarly, WSCI/BPEL refers to whatever
comes out of the current choreography standards efforts.  Alternative
technology stacks for Web services are currently offered by ebXML and
REST, and we may expect the Semantic Web and related efforts to develop
another alternative sometime in the future that formalises aspects of
Web services that are currently usually expressed in natural language.
There are, of course, plenty of common factors and overlaps between
these implementations of Web services, but none of them are likely to be
direct descendents of another unless considerable convergence occurs in
the future.