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RE: Nailing down the definition of "Web services" and the scope of WS A for the document

From: Cutler, Roger (RogerCutler) <RogerCutler@ChevronTexaco.com>
Date: Wed, 16 Apr 2003 18:17:05 -0500
Message-ID: <7FCB5A9F010AAE419A79A54B44F3718E026EF5C3@bocnte2k3.boc.chevrontexaco.net>
To: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, www-ws-arch@w3.org

I like this a lot.  I vote for "can be described", as you would no doubt
expect, because of my concern for including early binding scenarios.

-----Original Message-----
From: Champion, Mike [mailto:Mike.Champion@SoftwareAG-USA.com] 
Sent: Wednesday, April 16, 2003 3:16 PM
To: www-ws-arch@w3.org
Subject: Nailing down the definition of "Web services" and the scope of
WS A for the document



The chairs, editors, and team contacts have spent a couple hours today
discussing how to incorporate the good ideas that have come up while we
splashed around in the "what is a Web service" trout pond ... without
getting bogged down in the mud.  Here is my understanding of the
consensus, for discussion by the larger group.  The over-riding
intention is to push the WSA document ahead as efficiently as possible.

First, it probably makes sense to distinguish the generic term "Web
service" from the definition of the scope of the WSA.  To pick up a
point that Assaf
made: "How would you define the first few services put in place before
there

was reason to exchange WSDL definitions?"  We want to be able to say
that a relatively broad set of things can be considered "Web services"
but that the WSA is going to focus on a more restrictive set.

Here's a proposed defintion of the more general term:
"A Web service is an interface to an executable software agent that is
designed to be used by another software agent.  A Web service is
identified by a URI, and has a definition in a language sufficient to
describe the interface to developers of client agents. A software agent
interacts with a Web service in the manner prescribed by the formal
definition, using standard protocols."

A couple of clarifications:  first, this doesn't exclude RESTful,
information-exchange services; the "executable software agent" could be
an HTTP server.  Second, note the phrase "designed to be used by another
software agent."  We don't want to accept "screen-scraping" as even a
generic Web service technology; ANYTHING is a Web service under such a
defintion.

I (we?) think that this generic definition includes most of what
reasonable people would consider to be Web services without being
uselessly broad.  On the other hand, it's still probably too broad to be
the scope of the WSA effort -- it doesn't require SOAP, WSDL, or even
XML. Let's define a more restrictive subset, which we'll call "XML Web
services" [or perhaps "WSA-compliant Web services, although the word
"compliant" stocks a trout pond or two], upon which the WSA will focus:

"An XML Web service is an interface to an executable software agent that
is designed to be used by another software agent.  An XML Web service is
identified by a URI, and [CAN | MUST] have a formal definition in a
language that employs URI and XML. WSDL 1.2 is the "reference"
specification for an XML-based description language, but others are
possible.  A software agent interacts with an  Web service in the manner
prescribed by the formal definition, using XML based messages conveyed
by standard protocols. SOAP 1.2 is the "reference" specification for an
XML-based web service protocol, and the higher layers of the WSA model
will assume that it or an equivalent protocol  are employed."  

One clarification: I stuck in the references to SOAP and WSDL after the
discussions with the other editors, and would be glad to remove them ...
but I do think we need to make some reference to the centrality of SOAP
and WSDL in the WSA. 

There is one issue that the editors did not come to consensus on, and
for which we need input from the entire WG:  Is it sufficient to say
that the interface to an "XML Web service" CAN be described (or "is
capable of being
described") using a formal description language, or is it better to say
that it MUST be described in a machine-processable description language?


So, is this at least a good starting point for a consensus on how to
define "Web service" and "XML/WSA-compliant Web service" in the WSA
document?  Who on the WG can't live with it?  Who outside the WG wishes
to strenuously object? And what should the scope of the WSA require
...interfaces that CAN be described in a machine-processable language or
interfaces that MUST be described in a machine-processable description
language?  What other wordsmithing would anyone propose?
Received on Wednesday, 16 April 2003 19:17:31 GMT

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