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RE: Snapshot of Web Services Glossary

From: David Orchard <dorchard@bea.com>
Date: Sat, 22 Feb 2003 22:25:59 -0800
To: "'Walden Mathews'" <waldenm@optonline.net>, <www-ws-arch@w3.org>
Message-ID: <034301c2db04$6fe70b40$f10ba8c0@beasys.com>

Perhaps you should READ the W3C Web services architecture Usage Scenarios
document?  Scenario S070 is asynchronous messaging [1].  This is used by the
Use Case #2 [2].

Cheers,
Dave

[1] http://www.w3.org/TR/2002/WD-ws-arch-scenarios-20020730/#S070
[2] http://www.w3.org/TR/2002/WD-ws-arch-scenarios-20020730/#edi



> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Walden Mathews
> Sent: Saturday, February 22, 2003 4:38 PM
> To: Ugo Corda; Cutler, Roger (RogerCutler); www-ws-arch@w3.org
> Subject: Re: Snapshot of Web Services Glossary
>
>
>
> Sounds like what you really want is a definition of
> 'asynchronous', since
> that's the attribute sought, and then perhaps define
> 'synchronous' as the
> negation of the other.
>
> I'm not sure, though.  What other "use cases" do we have for the term
> 'synchronous'?  How did the term get on the glossary list?
>
> Walden
>
> ----- Original Message -----
> From: "Ugo Corda" <UCorda@SeeBeyond.com>
> To: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>;
> <www-ws-arch@w3.org>
> Sent: Saturday, February 22, 2003 12:31 PM
> Subject: RE: Snapshot of Web Services Glossary
>
>
> >
> > The way I have seen the concept of asynchronous Web services being
> understood most of the times is in term of client
> expectations regarding the
> interaction with a particular Web service. The expectations
> are such that
> the client can feel free to issue a request to the service at
> any time,
> regardless of whether the server is busy, is down at the
> present time, etc.
> After sending the request, the client can go about its other
> business, can
> go off line, can crash, etc. Still the client is confident
> that, some time
> after the server has been able to examine the client's
> request and send a
> response back, it will be able to get the server's response
> (assuming it -
> the client - is back online). Exactly how the underlying
> framework satisfies
> these expectations is implementation dependent (multiple threads,
> store-and-forward, queuing, etc.).
> >
> > Synchronous is any client-server interaction that cannot fulfill the
> expectations mentioned before.
> >
> > Ugo
> >
> > > -----Original Message-----
> > > From: Cutler, Roger (RogerCutler)
> > > [mailto:RogerCutler@chevrontexaco.com]
> > > Sent: Friday, February 21, 2003 7:10 PM
> > > To: Cutler, Roger (RogerCutler); Assaf Arkin; David Booth; Martin
> > > Chapman; www-ws-arch@w3.org
> > > Cc: Hugo Haas
> > > Subject: RE: Snapshot of Web Services Glossary
> > >
> > >
> > >
> > > Oh, perhaps I should express an opinion about the
> alternatives.  My
> > > druthers, for what they are worth, is that the "blocking"
> > > definition is
> > > the least desirable.  I base this on two factors: 1)I don't
> > > really know
> > > what it means in a world where applications can easily
> have multiple
> > > threads; 2)It does not seem to have any aspect of timeliness, or
> > > shortness of time, in it -- and my intuitive understanding of
> > > synchronous is that it has something to do with things
> happening in a
> > > timely manner.  I personally like the ones that are based
> on how fast
> > > things happen the best.
> > >
> > > That's my opinion, but I am MORE than willing to accept any of the
> > > approaches to the concept, as long as it is just one definition.
> > >
> > > -----Original Message-----
> > > From: Cutler, Roger (RogerCutler)
> > > Sent: Friday, February 21, 2003 9:05 PM
> > > To: 'Assaf Arkin'; David Booth; Martin Chapman; www-ws-arch@w3.org
> > > Cc: 'Hugo Haas'
> > > Subject: RE: Snapshot of Web Services Glossary
> > >
> > >
> > > Yeah, this is the approach to synchronous that I recall
> > > impressed me as
> > > being MOST different from the others.  I recall that there was a
> > > considerably more formal definition along these lines
> some months ago.
> > > Well, if not more formal at least longer, but along the same
> > > lines with
> > > the concept of agreeing about the time of day being the
> key factor.
> > >
> > > OK, there is the "blocking" thing, as in David's
> definition, there is
> > > this thing with agreeing about timing of clocks, and
> there have also
> > > been other definitions that were pretty formal but which
> ran along the
> > > lines of "how soon" things happen.
> > >
> > > IMHO there are at least three completely different
> understandings of
> > > what synchronous means floating around.  They all sound
> really good to
> > > me, but they are not the same.  I would REALLY like it if we
> > > could agree
> > > on one of them and make sure that when we use the word we
> > > agree that we
> > > are using the word in that sense.  Or, perhaps we could
> subset them
> > > somehow, as in synchronous(1) ... Synchronous(N).
> > >
> > > -----Original Message-----
> > > From: Assaf Arkin [mailto:arkin@intalio.com]
> > > Sent: Friday, February 21, 2003 12:26 PM
> > > To: David Booth; Martin Chapman; www-ws-arch@w3.org
> > > Cc: 'Hugo Haas'
> > > Subject: RE: Snapshot of Web Services Glossary
> > >
> > >
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: www-ws-arch-request@w3.org
> > > [mailto:www-ws-arch-request@w3.org]On
> > > > Behalf Of David Booth
> > > > Sent: Friday, February 21, 2003 10:09 AM
> > > > To: Martin Chapman; www-ws-arch@w3.org
> > > > Cc: 'Hugo Haas'
> > > > Subject: RE: Snapshot of Web Services Glossary
> > > >
> > > >
> > > >
> > > > At 04:35 PM 2/20/2003 -0800, Martin Chapman wrote:
> > > > >hmmm don't like the defn of synchronous:
> > > >
> > > > I struggled with this one, and I'm not sure my proposed
> wording is
> > > > ideal, but what I was trying to do was more clearly
> differentiate
> > > between
> > > > synchronous and asynchronous.   The old definition was
> very vague.
> > > >
> > > > Somehow we need to convey the idea that with "synchronous"
> > > > interactions the parties are synchronized in some way.
> (!)  This
> > > > could mean "at the same time", but in the case of two
> communicating
> > > > parties it generally means the
> > > > sending party waits for the receiving party to do something
> > > before the
> > > > sending party continues.  Thus, they are "synchronized".  I
> > > > couldn't figure
> > > > out any better way to precisely capture this.  Any ideas?
> > >
> > > Define that operation involves sending/receiving at initiator
> > > site, and
> > > receiving/sending at respondent site. Define "time" to be
> bound by T1
> > > (lower) and T2 (upper). I assume we can all agree to that.
> > >
> > > Given just sending and receiving primitives (e.g. TCP
> > > send()/receive()),
> > > initiator and respondent can agree on T1/T2 after concluding
> > > operation.
> > > With just these two communication primitives they can
> > > synchronize their
> > > clock within some resolution (but don't look for atomic
> clock type of
> > > synchronization here).
> > >
> > >
> > > > I agree that store-and-forward would NOT be
> synchronous, but I don't
> > > > see store-and-forward as the opposite of direct communication.
> > > > Communication can certainly be indirect (i.e., go through
> > > > intermediaries) but still be synchronous.  So although
> synchronous
> > > > communication is often direct, I don't see that as a
> distinguishing
> > > > characteristic.
> > >
> > > An interaction can be synchronous even if it uses some
> > > store-and-forward
> > > mechanism, even if both request and response are stored
> and forwarded.
> > >
> > > Test for synchronisity of interaction is something like that:
> > >
> > > If initiator sent request at time T1 then it can conclude that
> > > respondent did not start performing interaction before time T1 If
> > > initiator received request at time T2 then it can conclude that
> > > respondent did not continue performing interaction after
> time T2 (and
> > > vice versa)
> > >
> > > You can clearly see this is not true for asynchronous interaction.
> > >
> > > arkin
> > >
> > > >
> > > > >and
> > > > >the fact that the reply (if any) comes back on the same
> > > communication
> > > > >channel as the request.
> > > >
> > > > Interesting thought.  Must that always be true?  I
> could certainly
> > > > imagine an input-output operation in which the input uses one
> > > > communication channel
> > > > and the output uses another.  So again, I don't see this as a
> > > > distinguishing characteristic of synchronous communication.
> > > >
> > > > Anyone else have other suggestions for this definition?
> > > >
> > > >
> > > > --
> > > > David Booth
> > > > W3C Fellow / Hewlett-Packard
> > > > Telephone: +1.617.253.1273
> > >
> > >
> > >
> > >
> >
> >
>
>
Received on Sunday, 23 February 2003 01:30:57 GMT

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