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RE: Definition for a Web Service

From: Cutler, Roger (RogerCutler) <RogerCutler@chevrontexaco.com>
Date: Tue, 12 Aug 2003 04:04:46 -0500
Message-ID: <7FCB5A9F010AAE419A79A54B44F3718E01817F47@bocnte2k3.boc.chevrontexaco.net>
To: "Anne Thomas Manes" <anne@manes.net>
cc: "Www-Ws-Arch@W3. Org" <www-ws-arch@w3.org>

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 05:05:14 GMT

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