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Re: Definition for a Web Service

From: Anne Thomas Manes <anne@manes.net>
Date: Tue, 12 Aug 2003 07:09:06 -0400
Message-ID: <003701c360c2$269e8230$7101a8c0@TPX21>
To: "Cutler, Roger \(RogerCutler\)" <RogerCutler@chevrontexaco.com>
Cc: "Www-Ws-Arch@W3. Org" <www-ws-arch@w3.org>

+1. Thank you for articulating it so well.


----- Original Message ----- 
From: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>
To: "Anne Thomas Manes" <anne@manes.net>
Cc: "Www-Ws-Arch@W3. Org" <www-ws-arch@w3.org>
Sent: Tuesday, August 12, 2003 5:04 AM
Subject: RE: Definition for a Web Service


> 
> I'm not sure I understand what you say below -- the distinction between
> ports and endpoints is a bit fuzzy to me -- but let me explain why I
> think it is really important that a WS be identifiable by a URI and that
> it be specified clearly how it should be identified.  I'm going to be
> detailed so that you can see if I'm confusing some concepts or
> mislabelling anything.  I think I'm probably going to be agreeing with
> Frank's earlier posting, but if so I'm going to say it differently.
> 
> As I understand it, a Qname is a short string that identifies a Web
> service uniquely within the context of a WSDL file, but which depends on
> that context for the identification.  That is, a Qname taken outside the
> context of a WSDL file may be ambiguous.  So far OK with me -- no reason
> to carry around redundant baggage if it's not really needed.  So far no
> driver to have a URI.
> 
> In order to invoke a WS you obviously need a URI, but that is specific
> to the binding.  The HTTP and SMTP bindings of the X Web service may
> have entirely different URI's.  Again, no driver as yet to have a URI
> for the Web service itself.
> 
> But let's look at this in terms of audit trails.  Suppose a business
> transaction has gotten totally screwed up and some poor schnook is
> trying to untangle what happened in order to find out who didn't get
> paid.  Agent A and Agent B both got price quotes, ostensibly for the
> same thing.  Agent A got it from the HTTP binding of the X Web service,
> Agent B got it from the SMTP binding of the X Web service.  The URI's in
> the audit trail are completely different.  Did they get the same price
> quote?  The answer should be "Yes", because the Web service is supposed
> to give the same result, independent of binding.  So the audit trail
> needs to come up with "X", not just the URI's that were invoked.
> 
> OK, now I see a real strong reason to have a URI for the Web service
> itself -- and a SINGLE URI.  You don't want Agent A putting X into the
> audit trail and Agent B putting X', a different name for the same
> service.
> 
> So it doesn't bother me if the Web service is referred to inside the
> WSDL document by a Qname, but I think somebody needs to be real clear
> about how the single URI identifying the Web service is constructed.
> 
> Is that reasonable?
> 
> -----Original Message-----
> From: Anne Thomas Manes [mailto:anne@manes.net] 
> Sent: Monday, August 11, 2003 5:34 PM
> To: Cutler, Roger (RogerCutler)
> Cc: Www-Ws-Arch@W3. Org
> Subject: Re: Definition for a Web Service
> 
> 
> I'm not completely up to date on all the latest musings within WS-Desc,
> but I don't believe they equate a service with an endpoint. A service
> may offer multiple ports, and each port has a separate endpoint.
> 
> As long as a service has only one endpoint, then it's reasonable to use
> the endpoint URL to name the service. But if the service has multiple
> endpoints, which endpoint do you use as the service URI?
> 
> Based on the last set of questions they asked me about the issue, I
> think you're right -- I think that they decided that the wsdl:service
> Qname names the service, and if you want a URI to name the service then
> you should derive one from the Qname. I'm not especially happy with this
> decision, but I can live with it.
> 
> If that is the decision, then WS-Arch can claim that the service is
> identified by a URI derived from the wsdl:service Qname.
> 
> Anne
> 
> ----- Original Message -----
> From: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>
> To: "Anne Thomas Manes" <anne@manes.net>
> Sent: Monday, August 11, 2003 6:06 PM
> Subject: RE: Definition for a Web Service
> 
> 
> > I don't understand how what you say below goes together with your 
> > answer to Frank, in which you say that the URI should name the 
> > service, not the endpoint.  But my understanding has been that the 
> > WS-Desc WG is identifying the service with the endpoint.  I am 
> > confused, but I think that the understanding in the WSA-WG is that we 
> > are trying to arrange our terminology and concepts so that our 
> > "service" is at least close to the same thing as a WS-Desc service -- 
> > that is, I thought, an endpoint. But, as I said, I'm confused.
> >
> > I am pretty sure, however, that the TLA URI was deleted from the WS 
> > definition in a discussion where the word Qname came up.
> >
> > -----Original Message-----
> > From: Anne Thomas Manes [mailto:anne@manes.net]
> > Sent: Monday, August 11, 2003 4:53 PM
> > To: Cutler, Roger (RogerCutler); Jean-Jacques Moreau; Www-Ws-Arch@W3. 
> > Org
> > Subject: Re: Definition for a Web Service
> >
> >
> > Personally, I agree with the decision that a Web service must be 
> > described by WSDL. :-) But that doesn't mean that it won't also be 
> > described by other description languages. And as you say, that's 
> > beside the point.
> >
> > I'm not convinced that the discussion is completely closed in WS-Desc,
> 
> > and I think that if WS-Arch suggests that naming the service with a 
> > URI would be a good idea, the WS-Desc team would be happy to consider 
> > the input.
> >
> > Anne
> >
> > ----- Original Message -----
> > From: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>
> > To: "Anne Thomas Manes" <anne@manes.net>; "Jean-Jacques Moreau" 
> > <jean-jacques.moreau@crf.canon.fr>; <www-ws-arch@w3.org>
> > Sent: Monday, August 11, 2003 3:42 PM
> > Subject: RE: Definition for a Web Service
> >
> >
> > >
> > > We have -- and I personally think that this is unfortunate but it 
> > > does
> >
> > > represent a clear, consensus-driven decision by the WG that I 
> > > accept, albeit reluctantly -- limited the scope of what we are 
> > > willing to call
> >
> > > Web services and discuss in our architecture to thingies that are 
> > > described by WSDL and use SOAP -- as you can see in the definition. 
> > > That is, as far as we are concerned thingies described (only) by 
> > > text documents or DAML (unless DAML is somehow integrated into WSDL,
> 
> > > which I understand may not be an unreasonable expectation) are not 
> > > Web services. This was a highly contentious issue and the resolution
> 
> > > of it
> >
> > > was so difficult that I think it would take some sort of dramatic 
> > > change in the situation to convince people in the WG to reopen it.  
> > > As
> >
> > > I said, I don't like this resolution, but I would like reopening the
> 
> > > issue a WHOLE LOT LESS!
> > >
> > > That was not, however, the thrust of your message.  I personally 
> > > agree
> >
> > > that Web services are "important" resources and, for that reason, 
> > > should be identified by a URI.  I do not know how many others on the
> 
> > > WG would also agree, but I would guess at least some.  Or at least 
> > > would agree that "it sure would be nice" if Web services were 
> > > identified by a URI.
> > >
> > > It is my perception that the WG is, in effect, unwilling to do 
> > > things that are not compatible with what the WS-Desc WG is doing/has
> 
> > > done, and is also unwilling to tell the WS-Desc WG what to do.  I 
> > > would be very surprised, however, if anyone on the WSA-WG would 
> > > actually object
> >
> > > violently if the WS-Desc WG were somehow to decide to use URI's to 
> > > identify Web services.
> > >
> > > Obviously the comments above are my personal take on the situation 
> > > ...
> >
> > > Another member of the WG might view things quite differently and I 
> > > am in no way a spokesman for the WG.
> > >
> > > -----Original Message-----
> > > From: Anne Thomas Manes [mailto:anne@manes.net]
> > > Sent: Monday, August 11, 2003 1:02 PM
> > > To: Cutler, Roger (RogerCutler); Jean-Jacques Moreau; 
> > > www-ws-arch@w3.org
> > > Subject: Re: Definition for a Web Service
> > >
> > >
> > > I raised a discussion on the WS-Desc list suggesting that they 
> > > really should identify a Web service by a URI rather than just a 
> > > Qname. I was
> >
> > > a little surprised by the resistence to such a concept. I got the 
> > > sense that a lot of people didn't understand what in fact the URI 
> > > was meant to identify.
> > >
> > > I don't know what the end decision on the discussion was. I believe 
> > > it
> >
> > > was discussed at the last meeting.
> > >
> > > But I do think that the architecture group should have some 
> > > influence on the discussion. If the architecture group believes that
> 
> > > a Web service should be named by a URI, then the WS-Desc team should
> 
> > > provide
> >
> > > a means to capture that name in the WSDL description.
> > >
> > > From my perspective, a Web service is an "important" resource, and 
> > > as the Web Architecture says, all "important" resources should have 
> > > a URI. I also expect that a Web service may be described by a 
> > > variety of
> >
> > > description languages (WSDL, DAML, text documents, etc.) and so 
> > > there ought to be a means of referring to the Web service that 
> > > doesn't depend on just one description language (a URI derived from 
> > > the wsdl:service Qname).
> > >
> > > Anne
> > >
> > > ----- Original Message -----
> > > From: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>
> > > To: "Jean-Jacques Moreau" <jean-jacques.moreau@crf.canon.fr>;
> > > <www-ws-arch@w3.org>
> > > Sent: Monday, August 11, 2003 10:47 AM
> > > Subject: RE: Definition for a Web Service
> > >
> > >
> > > >
> > > > I think that this happened because of all the confusion about 
> > > > URI's and QNames.  As I understand it (and I am very willing to 
> > > > admit that
> >
> > > > I
> > >
> > > > understand this imperfectly), just about everyone concerned would 
> > > > be
> >
> > > > VERY happy to say that Web services are identified by URI's -- 
> > > > except that currently in WSDL they are identified by a Qname -- 
> > > > which is not exactly a URI but can be mapped to a URI.  This, at 
> > > > the
> >
> > > > least, adds a layer of confusion to any conversation on this 
> > > > subject.  I think that the basic thinking was that the 
> > > > "Web-related standards" would lead one
> > >
> > > > sort of inevitably to URI's, and that the detailed issues could be
> 
> > > > dealt with ... in the detailed sections, I guess.
> > > >
> > > > -----Original Message-----
> > > > From: Jean-Jacques Moreau 
> > > > [mailto:jean-jacques.moreau@crf.canon.fr]
> > > > Sent: Monday, August 11, 2003 3:45 AM
> > > > To: www-ws-arch@w3.org
> > > > Subject: Definition for a Web Service
> > > >
> > > >
> > > >
> > > > Thanks for the new draft; obviously, this is the result of a lot 
> > > > of efforts!
> > > >
> > > > Regarding the new definition for a Web Service: apart from being 
> > > > more specific (WSDL, SOAP, HTTP), which I like, the other major 
> > > > difference seems to be that a Web Service is no longer identified 
> > > > by
> >
> > > > a URI. Is this
> > > >
> > > > intentional? Shouldn't this be added back?
> > > >
> > > > <previousDefinition>
> > > > A Web service is a software system identified by a URI [...]. 
> > > > </previousDefinition>
> > > >
> > > > Comments?
> > > >
> > > > Jean-Jacques.
> > > >
> > > > Champion, Mike wrote:
> > > >
> > > > > Update from the W3C publication team:
> > > > >
> > > > > New WD of "Web Services Architecture" Document is available at :
> 
> > > > > http://www.w3.org/TR/2003/WD-ws-arch-20030808/
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
> 
> 
> 
> 
Received on Tuesday, 12 August 2003 07:09:12 GMT

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