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RE: Some proposed definitions of "web service" based on the call toda y

From: Anne Thomas Manes <anne@manes.net>
Date: Sun, 20 Apr 2003 12:40:10 -0400
To: "Katia Sycara" <katia@cs.cmu.edu>, "Newcomer, Eric" <Eric.Newcomer@iona.com>, "Christopher B Ferris" <chrisfer@us.ibm.com>
Cc: <www-ws-arch@w3.org>
Message-ID: <ECEDLFLFGIEENIPIEJJPIELCEAAA.anne@manes.net>
+1 -- from the client's perspective, the Web service did not change.

I think Eric's concern is that the Web services framework doesn't define the
object model of the agent that implements the service. Hence I think we need
to clearly articulate that we intentionally don't define the object model.

This is a major feature of the Web services framework. By not defining the
object model, we ensure that any application, regardless of its object
model, can use the Web services framework. We're talking about clean
separation of interface from implementation. The interface completely hides
the details of the implementation. It is up to the runtime system that
implements the Web services framework to map the interface to the
implementation. ne

An
  -----Original Message-----
  From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
Behalf Of Katia Sycara
  Sent: Sunday, April 20, 2003 11:59 AM
  To: Anne Thomas Manes; Newcomer, Eric; Christopher B Ferris
  Cc: www-ws-arch@w3.org
  Subject: RE: Some proposed definitions of "web service" based on the call
toda y


  I support the view articulated by Anne.
  The question that is then raised is the following: for the same service
description, one could change the implementation of the "underlying" agent.
If the results of agent execution remain the same under the two agent
implementations, do we say the service did not change?
    I would favor this view.
   --Katia
    -----Original Message-----
    From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
Behalf Of Anne Thomas Manes
    Sent: Sunday, April 20, 2003 8:31 AM
    To: Newcomer, Eric; Christopher B Ferris
    Cc: www-ws-arch@w3.org
    Subject: RE: Some proposed definitions of "web service" based on the
call toda y


    But it's still inappropriate to say that the Web service is only the
interface. The interface doesn't perform the service. If you only have an
interface and not an agent, then the service cannot be performed. You must
have both for it to be a working Web service.

    Anne
      -----Original Message-----
      From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
Behalf Of Newcomer, Eric
      Sent: Sunday, April 20, 2003 7:50 AM
      To: Christopher B Ferris
      Cc: www-ws-arch@w3.org
      Subject: RE: Some proposed definitions of "web service" based on the
call toda y


      Yes, the agent performs the service.  But what we are defining in Web
services specifications, and therefore in the Web services architecture, is
not the agent but the *description* of the service.  This is very different
from CORBA for example where the "agent" was defined.
        -----Original Message-----
        From: Christopher B Ferris [mailto:chrisfer@us.ibm.com]
        Sent: Saturday, April 19, 2003 8:59 PM
        To: Newcomer, Eric
        Cc: www-ws-arch@w3.org
        Subject: RE: Some proposed definitions of "web service" based on the
call toda y



        I agree that there's nothing in the WSDL or SOAP that necessarily
says
        what the agent has to be, but nonetheless, it is the agent that
performs the
        service.

        Cheers,

        Christopher Ferris
        Architect, Emerging e-business Industry Architecture
        email: chrisfer@us.ibm.com
        phone: +1 508 234 3624

        "Newcomer, Eric" <Eric.Newcomer@iona.com> wrote on 04/19/2003
03:12:45 PM:

        > I still have the problem with defining the agent as the service.
The service is mapped or
        > transformed onto the agent.  Saying that a Web service is an
interface to an agent, a
        > representation of an agent, or a description of an agent are all
ok with me, but I can't (for
        > example) see anything in SOAP, WSDL, etc. that defines what the
agent is or has to be.
        > -----Original Message-----
        > From: Christopher B Ferris [mailto:chrisfer@us.ibm.com]
        > Sent: Friday, April 18, 2003 8:00 AM
        > To: www-ws-arch@w3.org
        > Subject: Re: Some proposed definitions of "web service" based on
the call toda y

        >
        > I would prefer that we not include references to version numbers
in the definition, as these will
        > change over time. I think that the acronyms should suffice.
Secondly, I thinn that qualifying SOAP by
        > calling out the XML Infoset and processing model suggests that
other aspects of SOAP are either
        > not used, or not allowed, or who knows what. I think that it is
sufficient to say just SOAP. Finally, since
        > we have spent some time discussing the various types of ways in
which people have been using the term,
        > I felt that it is probably worthwhile that we share some of these
alternate uses with the readers of the
        > WSA and give them a little more background.
        >
        > How 'bout this:







 > -------------------------------------------------------------------------
        > The term "Web service" has been used to refer to a wide variety of
things,
        > and it is clear that not all people share the same understanding
and definition.
        > For some, it has meant simply the exchange of XML over the Web,
typically using HTTP.
        > For others, it has meant simply the exchange of SOAP messages,
typically using HTTP,
        > or some software component that has been described using WSDL. In
a sense, all of these
        > things might be considered to be "Web services", and the Working
Group does not
        > preclude the use of the term to describe these sorts of things.
Nevertheless, for
        > the purposes of this document, we will define the term Web
services as follows:
        >
        > [Definition: Web service - an executable software agent that is
identified by
        > a URI and whose interface and binding(s) are described using WSDL.
Other software agents
        > interact with a Web service in a manner prescribed by its WSDL
description, using SOAP.]
        >








> --------------------------------------------------------------------------
-------------------------------------------------------------------------
        >
        > Now, this definition probably deserves some further explanation in
order to say things like
        > "there's nothing
        > to preclude the use of other protocols (than SOAP) to interact
with a Web service... for the
        > purposes of this document, we simply
        > aren't going to go there" and "while the definition requires the
use of WSDL, it does not preclude
        > the use of
        > other technologies or XML vocabularies for its description.
however, for the purposes of this document, we
        > aren't going to go there..."
        >
        > Again, it might be nice to solve the equation for all possible
solutions to WS = U + Xd + Xm (a
        > web service is identified
        > by a URI and described using XML and interacted with using XML
messages) IMO this represents a daunting
        > task. We should be focused on defining an architecture that
leverages the technologies being developed
        > in our sibling WGs in the Web Services Activity in its
realization.
        >
        > Cheers,
        >
        > Christopher Ferris
        > Architect, Emerging e-business Industry Architecture
        > email: chrisfer@us.ibm.com
        > phone: +1 508 234 3624
        >
        > www-ws-arch-request@w3.org wrote on 04/17/2003 05:36:27 PM:
        >
        > >
        > > Whew, that was fun :-(  Although it got better when we stumbled
on the
        > > "instant straw poll in IRC" idea; we should do that more often.
I'd say
        > > that in general, anyone who has the "floor" in the speaker queue
may propose
        > > one of those by typing the question into IRC; those not on IRC
can ask to
        > > have their vote recorded by someone who is.
        > >
        > > Let me throw out some proposals that reflect the various
opinions I heard
        > > today; without my co-chair hat on, I could live with either of
them:
        > >
        > >
===========================================================================
        > > The term "web service" is used in a wide variety of ways by
different
        > > people, and we will not presume that the definition used here is
consistent
        > > with all of them.  Nevertheless, for the purposes of this
document, we will
        > > use the term to mean the following: 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 MUST be [capable of being ?] formally
defined in
        > > WSDL 1.2.  A software agent interacts with an  Web service in
the manner
        > > prescribed by the formal definition, using the XML Infoset and
processing
        > > model defined by SOAP 1.2.
        > >
        > > [Chris said some things about SOAP being general enough to
describe any
        > > reasonable "web service" interaction that I didn't capture very
well ...
        > > maybe he can refresh my memory.]
        > >
        > >
==========================================================================
        > >
        > > The term "web service" is used in a wide variety of ways by
different
        > > people, but there is a rough consensus along the following
lines: 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 that is consistent with the description, using
standard
        > > protocols.
        > >
        > > That definition of "web service" is not sufficiently precise or
rigorous for
        > > architectural purposes, however.  We will use a more restrictive
term to
        > > describe the scope of the architecture described here:
"Extensible XML Web
        > > Services", abbreviated XWS.   the purposes of this document, we
will use the
        > > term to mean the following: An XWS is an interface to an
executable software
        > > agent that is designed to be used by another software agent.  An
XWS is
        > > identified by a URI, and MUST be capable of being formally
defined in WSDL
        > > 1.2.  A software agent interacts with an  Web service in the
manner
        > > prescribed by the formal definition, using the XML Infoset and
processing
        > > model defined by SOAP 1.2."
        > >
        > > ["XWS" is essentially a placeholder for some term ... I don't
care what it
        > > is, but it must specifically describe the "MUST" constraints
specified by
        > > the WSA.]
        > >
        > >
==========================================================================
        > > Of course, improved definitions are solicited.
        > >
Received on Sunday, 20 April 2003 12:38:57 GMT

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