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RE: Snapshot of Web Services Glossary

From: Martin Chapman <martin.chapman@oracle.com>
Date: Mon, 24 Feb 2003 11:06:43 -0800
To: "'David Orchard'" <dorchard@bea.com>, <www-ws-arch@w3.org>
Message-ID: <003601c2dc37$deff4ae0$488e1990@us.oracle.com>

David,

I certainly this a while ago and concluded that it didn't help much.
What does "A sender sends a message asynchronously to a receiver
expecting some response at a later time" mean. 
Doesn't really define asynchronous does it!
Waiting for "some reponse at a later point in time" is true for all
request/response interactions.

Martin.

> -----Original Message-----
> From: www-ws-arch-request@w3.org 
> [mailto:www-ws-arch-request@w3.org] On Behalf Of David Orchard
> Sent: Saturday, February 22, 2003 10:26 PM
> To: 'Walden Mathews'; www-ws-arch@w3.org
> Subject: RE: Snapshot of Web Services Glossary
> 
> 
> 
> 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 Monday, 24 February 2003 14:07:11 GMT

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