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RE: Separate concepts for "service" and "targetResource?" (was RE : /service/@targetResource ?)

From: Champion, Mike <Mike.Champion@SoftwareAG-USA.com>
Date: Wed, 21 May 2003 21:29:46 -0400
Message-ID: <9A4FC925410C024792B85198DF1E97E405B81CAF@usmsg03.sagus.com>
To: www-ws-arch@w3.org



> -----Original Message-----
> From: Walden Mathews [mailto:waldenm@optonline.net]
> Sent: Wednesday, May 21, 2003 8:40 PM
> To: Ugo Corda; Champion, Mike; www-ws-arch@w3.org
> Subject: Re: Separate concepts for "service" and 
> "targetResource?" (was
> RE : /service/@targetResource ?)
> 

> I suppose this question is to Mike, but allow me to answer 
> out of sheer
> fascination.  NO!  Implementations are, by design, at least 
> one level of
> indirection away from resources.  

As far as I know, a "resource" is anything with identity that can
meaningfully be accessed via the Web.  What the WSDL people call a
targetResource has identity (it's a specific piece of code that performs a
well-defined operation) and it is accessed via the Web (or at least by Web
gateways).  For example, a specific printer attached to a mainframe that can
be accessed by a HTTP/SOAP gateway is a "resource" with identity, or at
least the specific software agent that "drives" the printer from the Web
service point of view is a Web resource.  

If this is too confusing from the Webarch perspective we can drop the term
"resource" and just refer to the software drivers as "agents."  That's OK
with me, but the WSD group specifically chose the term "resource" because it
seemed to fit the Webarch concept of a "resource" ... and has a URI that
WSDL can use to determine equality of identity.

> The URI binds to the meaning, not to the code.

Hmm, that's an interesting point of view.  We did talk about this a bit ...
clearly the targetResource is not a specific bag of bits, because it's
identity is defined by the operations it performs on a specific "thing" that
is hard to define.  In the printer example, the "thing" is the physical
printer, but printers aren't really Web resources in the Webarch are they?
It gets messier if the "thing" is some piece of software: if we rewrote the
Web service interface so that it is in Java rather than C#, has its
identity/URI changed?  I don't think so, so in that sense I agree with
Walden ... but on the other hand its manifestation *is* a piece of code that
one runs.  Unless we want to get into the idea that a specific piece of code
is the "representation" of the abstract resource that defines its
functionality, I think it's easier to say that the agent sitting on the
"turtle" is the targetResource.   But if WSD is happy calling it targetAgent
rather than "resource", I'm happy ... so long as something has a URI that
does what WSDL needs to do with it.  
Received on Wednesday, 21 May 2003 21:29:47 GMT

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