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RE: A Priori Information (Was Snapshot of Web Services Glossary )

From: Assaf Arkin <arkin@intalio.com>
Date: Wed, 26 Feb 2003 12:02:12 -0800
To: "Cutler, Roger \(RogerCutler\)" <RogerCutler@chevrontexaco.com>, "David Orchard" <dorchard@bea.com>, "Hugo Haas" <hugo@w3.org>
Cc: "David Booth" <dbooth@w3.org>, <www-ws-arch@w3.org>
Message-ID: <IGEJLEPAJBPHKACOOKHNKECMDEAA.arkin@intalio.com>



> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Cutler, Roger (RogerCutler)
> Sent: Wednesday, February 26, 2003 9:50 AM
> To: David Orchard; Hugo Haas
> Cc: David Booth; www-ws-arch@w3.org
> Subject: RE: A Priori Information (Was Snapshot of Web Services Glossary
> )
>
>
>
> I think that the term "a priori" really only has one rigorous meaning,
> and that is (as posted by Ugo 2/19):
>
> A priori: relating to or derived by reasoning from self-evident
> propositions.

That's one definition, but all the ones I've read [1] seem to imply that a
priori knowledge is one that is not based on facts, such as self-evident,
intuitive or whatever reasoning you had and want to validate.

So a use case would go like that:

- I think this service will give me the time of day (a priori)
- I send a request, get a response, validate/invalidate my assumption

So, to further confuse the reader, if I had a definition of the service that
I want to interact with, I would say that's a priori knowledge. It's not
self evident or intuitive, but it's reasoning based on the service
definition. It's not validated.

I send a request, get a response, validate my assumption based on that
response and now my knowledge is no longer a priori.

On the other hand, if I have an end-point with no idea what it does, send a
message and get some response back, then I learn what the service does
without a priori knowledge. (End-point is considered prior knowledge in this
context)

In other words, using a WSDL definition to interact with a service is a
priori knowledge, but just sending some empty message and getting a response
is no a priori knowledge with prior knowledge.

And before REST advocates interject, the same holds true for protocol listed
in the URL. Assuming that a URL starting with http: implies an HTTP server
at that end is a priori knowledge. We validate it by sending an HTTP request
and seeing whether we get any HTTP response or some other response (no HTTP
server here, go away!) or no response (no TCP server here, have a nice day).

arkin

[1] http://dictionary.reference.com/search?q=a+priori&r=3

>
> However, as David has pointed out, the objective here is really to deal
> with the issue that has been raised.  We are, I believe, suggesting that
> we don't really have to define the term in the Glossary if we don't
> intend to use it in the architecture document, but we do have to deal
> with the issue.
>
> I think that the underlying assumption here, at least in my mind and I
> think in a number of others, is that the term was used somewhat
> carelessly in the charter and that whoever wrote it really meant
> "prior".  The statement is much easier to understand if one substitutes
> "prior" for "a priori", and it seems to have a real function that way.
> That is, if we interpret it in this way we think that we are being
> consistent with, and responding to, the intended meaning of the charter.
> I think that if we get embroiled in a lengthy discussion of the term "a
> priori" we will, in fact, not be responding to the intent of the
> charter.
>
> At the very least, if we answer the issue in this way it puts the ball
> in the other court.  That is, if the framers of the charter REALLY meant
> something other than "prior" they can tell us so, since we have made it
> very clear that this is our best understanding of what they meant at
> this moment.
>
> If we take this path, however, I think we definitely do NOT want to put
> a definition of "a priori" into the glossary that says it is equivalent
> to "prior".  That would simply be propagating confusion.
>
> -----Original Message-----
> From: David Orchard [mailto:dorchard@bea.com]
> Sent: Wednesday, February 26, 2003 10:47 AM
> To: Cutler, Roger (RogerCutler); 'Hugo Haas'
> Cc: 'David Booth'; www-ws-arch@w3.org
> Subject: RE: A Priori Information (Was Snapshot of Web Services Glossary
> )
>
>
> I dunno.  I think that the term "A priori" should be defined in a
> rigorous way.  Can somebody summarize the differences between the
> definitions that have been championed?
>
> Dave
>
> > -----Original Message-----
> > From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> > Behalf Of Cutler, Roger (RogerCutler)
> > Sent: Wednesday, February 26, 2003 7:37 AM
> > To: Hugo Haas
> > Cc: David Booth; www-ws-arch@w3.org
> > Subject: RE: A Priori Information (Was Snapshot of Web
> > Services Glossary
> > )
> >
> >
> >
> > Well, the suggestion was NOT to put anything in the glossary for this
> > term and to use the verbiage below as a response to the issue.
> >
> > I'm not sure if we have anything explicit in the requirements about
> > supporting late binding, but it seems to me that a number of people on
>
> > the WG consider this important and that this was the sense of the
> > statement in the charter.
> >
> > -----Original Message-----
> > From: Hugo Haas [mailto:hugo@w3.org]
> > Sent: Wednesday, February 26, 2003 9:34 AM
> > To: Cutler, Roger (RogerCutler)
> > Cc: David Booth; www-ws-arch@w3.org
> > Subject: Re: A Priori Information (Was Snapshot of Web
> > Services Glossary
> > )
> >
> >
> > * Cutler, Roger (RogerCutler) <RogerCutler@chevrontexaco.com>
> > [2003-02-24 10:41-0600]
> > > OK, we've kicked this term around enough so that it seems
> > pretty clear
> >
> > > that it is not going to be a quick kill to get consensus on
> > a general
> > > definition, and I think David is absolutely correct: we need to
> > > address the issue itself, but not necessarily this term as
> > a general
> > > concept.
> > >
> > > So I suggest something along the following resolution to resolve the
> > > issue:
> > >
> > > "The WG is not currently using the term "a priori
> > information" in the
> > > reference architecture, so we do not feel a need to come to an
> > > agreement about the meaning of the term in general.  In the
> > specific
> > > context in which it is used in the group charter, we
> > understand it to
> > > mean "prior information".  We interpret this as a
> > requirement that the
> >
> > > architecture support late binding."
> >
> > I am happy to put such a statement in the glossary. However, I think
> > that we should add something (or a placeholder) in the WSA to talk
> > about it. Maybe just to say what you are saying here.
> >
> > However, I was wondering if we had actually a requirement about this
> > before saying "We interpret this as a requirement that the
> > architecture support late binding."
> >
> > AC004 and AR004.2 read[1]:
> >
> > |   AC004
> > |          does not preclude any programming model.
> > |
> > |          + AR004.2 is comprised of loosely-coupled components and
> > their
> > |            interrelationships.
> >
> > I think that this is the one that has been discussed when there were
> > late binding discussions, but I don't think that it explicitely calls
> > out for it. Maybe we are missing a requirement then.
> >
> > Or have I missed something in the requirements document?
> >
> > Regards,
> >
> > Hugo
> >
> >   1. http://www.w3.org/TR/2002/WD-wsa-reqs-20021114#AC004
> > --
> > Hugo Haas - W3C
> > mailto:hugo@w3.org - http://www.w3.org/People/Hugo/
> >
> >
> >
Received on Wednesday, 26 February 2003 15:04:46 GMT

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