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From: Mark Baker <distobj@acm.org>
Date: Wed, 31 Jul 2002 22:15:45 -0400
To: Hao He <Hao.He@thomson.com.au>
Cc: www-ws-arch@w3.org
Message-ID: <20020731221545.C12993@www.markbaker.ca>


On Thu, Aug 01, 2002 at 11:22:49AM +1000, Hao He wrote:
> hi, Mark,
> First, I see URIs as identifiers to logical concepts, which can exist before
> its representations. For example, when go buy a car, you can know before

Presumably you meant "can't" ...

> hand the different states you will experience. That is why you would take
> your credit card with you.

Right, *you* can't know all the states, but you can defer to the dealer
who knows more, and it can defer to the manufacturer who knows the rest
of it, etc..

So all I need to say is;

"I'm going to <a href="http://www.some-dealership.com/car-purchase">buy
a car</a>"

in order to delegate.

>  Therefore, there is a need to describe those
> logical state transitions long before the actual URI representation.    

I'll answer that indirectly ...

It's true that not everybody who buys a car follows the same set of
state transitions.  This is equivalent to links being generated either
client-side with a GET form, or server-side based on some POSTed data.
But in those cases, it's impossible to know the transition a priori
because the necessary information hasn't been provided.  So the best
information is what's available in the form.

I think a use case would help, if you want to get into this in detail
now.  Perhaps we could take it offline too.  It sounds interesting,
even if I don't exactly know what you're getting it. 8-)

> Second, one should allow late binding between a URI and its physical
> representation.  Such binding is very common and should be described in a
> standard way.  For example, a physical representation is only available
> within a time window.  

Are you referring to resources such as "Highway 401 from 16:00 to
19:00"?  Or do you mean that a GET might only result in something
useful within a time window?  I suppose that the latter could be
expressed in WSDL, but I don't know that many services would need to
use it.

Mark Baker, CTO, Idokorro Mobile (formerly Planetfred)
Ottawa, Ontario, CANADA.               distobj@acm.org
http://www.markbaker.ca        http://www.idokorro.com
Received on Wednesday, 31 July 2002 22:15:48 UTC

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