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On Thu, 2003-07-24 at 05:55, Tim Bray wrote:
> John Cowan wrote:
>
> > There's no doubt that representations are what's emitted.
> > The difference between Pat's 1) and 2) is whether GETting
> > http://www.ihmc.us/users/phayes/Yosemite.html returns a representation
> > of a *document about Yosemite* (reading 1) or whether it returns a
> > representation of *Yosemite* (reading 2). Either is plausible, but the
> > difference is as fundamental as the difference between George Washington
> > and a U.S. quarter.
>
> Questions: (a) can software detect the difference?
Yes, from context - in what context is the URI used ? As an identifier
for a non-retrievable resource or as the address of a retrievable
resource. The URI by itself cannot tell you that, but the context in
which it is used can. This is the principle behind the subject / subject
indicator distinction in topic maps.
> (b) does the difference have any effect on the behavior of the system?
>From a topic map perspective, the answer is "not really" in either case,
two topics which match in subject or subject identifier are considered
to be about the same thing (a heuristic which is fairly simplistic given
that a resource may represent different things to different people, but
a necessary one to keep the model processable). Importantly if topic A
has a URI as its subject and topic B has the same URI as its subject
indicator, they are *not* merged - one represents the retrievable
resource and the other represents the subject described by the
retrievable resource.
Cheers,
Kal
--
Kal Ahmed, Techquila
Standards-based Information Management
e: kal@techquila.com
w: www.techquila.com
p: +44 7968 529531
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