[R3xx] Requirements Section "4.2 Simplicity and Stability" -- com parison with SOAP1.1.

Following is an assessment of how well SOAP1.1 [1] fulfills our current 
(editor's copy) requirements document [2], specifically in the section 
"4.2 Simplicity and Stability".  The sections are reviewed in the order
they appear in the requirements text.

Apologies for not sending this message out sooner for review,
since it appears we are on the agenda for today's telcon.

Best Regards,
David Ezell
Stuart Williams


[1] http://www.w3.org/TR/SOAP/
[2] http://www.w3.org/2000/xp/Group/xp-reqs-05

============  Section 4.2  Simplicity and Stability ============
 
=== Preamble (text preceding R307)

SOAP1.1 supports the design space suggested in the preamble.  However, the
section is a preamble and not a requirement.  

=== R307

It cannot be proven that SOAP1.1 would not address this requirement; however,
the requirement calls out usage scenarios as tools to prove suitability.
Since the usage requirements themselves are under consideration, we can only
suggest that the XML Protocol R307 will help outline requirements which are
more widely "suitable" than those used in the design of SOAP1.1,  and further 
suggest that SOAP1.1 might fall short of fulfilling these requirements.
 
More specifically, SOAP1.1 has only limited usage scenarios, and as such
falls short of R307.
 
=== R308

The SOAP1.1 specification succeeded to some extent in supporting modularity,
especially modularity in terms of unforeseen architectural components which
can be supported through constructs such as the "Header" and "Body" elements,
or in SOAP encoding rules.  However, this modularity seems weaker than that
specified in the XML Protocol requirements.  Further, SOAP1.1 doesn't appear
to have much support for "layering".  Such support arguably requires a 
clear architecture, promised in XML Protocol requirements (R300) but missing 
in SOAP1.1.
 
=== "Postamble" (text following R308)

Since this section is not a requirement per se, the analysis for SOAP1.1
does not apply (even though it *used* to be part of DR305).
	 
=== R300

In SOAP1.1, "1. Introduction", SOAP specifically declines to define an
architecture, abstract or otherwise:  "SOAP does not itself define
any application semantics... or implementation semantics...; rather it
defines ... a modular packaging model and encoding mechanisms...".  
 
The semantics mentioned are some of the key elements in the abstract
models which are being introduced.  Clearly, SOAP1.1 doesn't satisfy
XML Protocol requirements in this regard.  Please note that these
semantics are also the focal point of the ongoing "usage scenario"
work being done by the WG.  Also note that "application" semantics
are clearly out of scope (as they are for SOAP1.1), whereas "operational" 
semantics of a messaging system are in scope.
 
=== R301

SOAP1.1 conforms.
 
=== R301a

Since SOAP1.1 defines only a "modular packaging model" and "encoding
mechanisms",
conformance with SOAP1.1 can be viewed as "validation" conformance (as in
DTD or Schema validation).  "XML Protocol requirements" is suggesting a more
rigorous conformance test which includes semantics defined in in-scope usage
scenarios, i.e. certain types of behavior.
 
=== R302

SOAP1.1 defines a vocabulary with certain types of extensibility.  XML
Protocol requirements declare a need for extensibility which supports
"decentralized extensibility without prior agreement".  It's not clear
whether the types of extensiblity in SOAP are adequate for this requirement.
 
=== R304

A central point of R304 is really that the WG will define certain usage
scenarios
as in-scope.  It is not yet certain whether SOAP1.1 will be adequate for these
scenarios.  SOAP1.1 does appear to support the RPC flavor of exchange.
Other scenarios are not so clear.  (See comments in R307).
 
=== R306

SOAP1.1 does not directly address deployment issues; but may indeed satisfy 
this requirement, with the qualification that it does not address a "full 
spectrum" of deployment environments.  Rather, it addresses the HTTP common 
web-server/web-browser situation.

=== R309

While SOAP1.1 may indeed be adequate for some simple exchanges usable
on small systems, hopefully XML Protocol will do a better job of
addressing these needs explicitly.

Received on Wednesday, 31 January 2001 11:29:52 UTC