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Re: Definition for a Web Service

From: Sanjiva Weerawarana <sanjiva@watson.ibm.com>
Date: Tue, 12 Aug 2003 22:46:03 +0600
Message-ID: <032301c360f1$3974da10$02c8a8c0@lankabook2>
To: "Anne Thomas Manes" <anne@manes.net>, "Www-Ws-Desc@W3. Org" <www-ws-desc@w3.org>

Please see my reply to this thread on the ws-arch list. I don't think
the proper level of common understanding of the problem exists yet.

Sanjiva.

----- Original Message -----
From: "Anne Thomas Manes" <anne@manes.net>
To: "Www-Ws-Desc@W3. Org" <www-ws-desc@w3.org>
Sent: Tuesday, August 12, 2003 9:51 PM
Subject: Fw: Definition for a Web Service


>
> Can you tell me whether the team has made a decision regarding the issue I
> raised about a service URI? Please see the use case that Roger Cutler
> describes below.
>
> Regards,
> Anne
>
> ----- 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 11:04 AM
> Subject: RE: Definition for a Web Service
>
>
> >
> > Well, if you agree -- can you tell me if the WS-Desc WG has, or is
> > planning to, define normatively the way to identify the X below with a
> > URI?  I think that's kind of important.
> >
> > -----Original Message-----
> > From: Anne Thomas Manes [mailto:anne@manes.net]
> > Sent: Tuesday, August 12, 2003 6:09 AM
> > To: Cutler, Roger (RogerCutler)
> > Cc: Www-Ws-Arch@W3. Org
> > Subject: Re: Definition for a Web Service
> >
> >
> > +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/
> > > > > >
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Received on Tuesday, 12 August 2003 12:46:24 GMT

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