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

From: John Crupi <John.Crupi@Sun.COM>
Date: Wed, 16 Apr 2003 22:04:31 -0400
To: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>
Cc: www-ws-arch@w3.org
Message-id: <3E9E0BAF.3010007@sun.com>

Since you asked...

I know I'm late to jump in, but a few comments:

1. "A Web service is an interface to an executable software agent..."
    >> I think the 'software agent' concept will confuse many.

2. "A Web service is an interface to an executable software agent..."
    >> Are we saying a web service is not a service, but is an 
interface. Isn't a web service a service with an exposed interface?

3. "...designed to be used by another software agent."
    >>Why not say 'client' instead of agent and give examples of a 
client. Or maybe the fact that the interface is exposed implies that is 
can be used by others.

4. Also, why have a "web service" and an "XML web service" definition. 
What is wrong with taking the XML web service definition and making it 
the "WSA-compliant Web service" definition.

Just some thoughts...


John Crupi
Distinguished Engineer/Chief Java Architect
Sun Software Services
Sun Microsystems, Inc.
Cell: 301-526-7890
AIM: JohnCrupi

Champion, Mike wrote:

>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
>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 22:06:57 UTC

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