[topicmapmail] Identities and names (WAS - A somewhat new topic maps format)

[Daniel Rivers-Moore]

Peter

I think you are underestimating the ability of the RDF community to
slide between seeing the referent of a URI to be a resource on a
computer system to which the URI resolves, and seeing it as a "resource"
in a much broader sense, namely any thing or concept. RDF does not make
the distinction that XTM makes between what the XTM 1.0 Conceptual Model
calls a Resource (something addressable on a computer system) and what
it calls a "Non-addressable Subject". RDF uses the word 'resource' to
cover both, and uses URIs as names for both.

So, rereading the passage you quote below, which says that "any
assertion of a graph implicitly asserts that all the names in the graph
actually refer to something in the world", my conclusion would be:

"Beware of just making up URIs that don't *refer* to anything"

rather than

"Beware of just making up URIs that don't *resolve* to anything"


One of the problems RDF has is that it does not provide any algorithm
for determining what the URI refers to (there is no "protocol for
dereferencing" the URIs in an RDF triple). They *may* refer to the
resource to which they also resolve (if there is one), or they may refer
to something that resource (if there is one) has a close relationship
with (e.g. a person whose email address is used as the referencing URI).
On the other hand, if there is no resource to which they resolve, they
may refer to some resource to which they *did* resolve at some time in
the past, or some resource the author believed would shortly come into
existence, or ..., or ..., or any other thing in the world (including
non-addressable "resources/subjects" like people, places, mountains or
ideas) that the author chose to use that URI as a name for.

In this regard, an interesting discussion went on throughout July on the
W3C Technical Architecture Group discussion forum, with the subject
"Meaning of URIs in RDF documents"
(http://lists.w3.org/Archives/Public/www-tag/2003Jul/0159.html). I'll
just pull our one tiny snippet from this thread which, I think,
illustrates the problem (for RDF):

Tim Berners-Lee says:
If you take the case of an identifier for pat hayes <phayes@ihmc.us>,
for example, the non-logician would consider that it identified one
person and get on with their lives

And Pat Hayes replies:
The logician can say that also: it is the assertion that a single person
exists who has that name. But (1) that is not the same as saying that
the name - all by itself - "identifies" a single person (or, well, maybe
it is: but if so, then other things said about URIs and resources are
wrong) and (2) in fact, they don't assume that and get on with their
lives. Sometimes they assume it indicates a person, sometimes a mailbox,
sometimes a computer: it depends on the context.=20


Topic Maps have, I believe, made considerable steps beyond the situation
RDF finds itself in in this regard, and the work Bernard, Murray, and
others on this list are urging us to take forward, will hopefully make
still further progress

Best regards

Daniel

-----Original Message-----
From: Peter P. Jones [mailto:ppj@concept67.fsnet.co.uk]=20
Sent: 08 August 2003 09:58
To: topicmapmail
Subject: Re: [topicmapmail] Identities and names (WAS - A somewhat new
topic maps format)

On 7 Aug 2003 at 19:26, Peter P. Jones wrote:

> On 7 Aug 2003 at 15:08, Murray Altheim wrote:
>=20
> [...]
> >=20
[...]
>=20
> (Not including Steve Pepper's argument for distinguishing subject
> location from mere resource location where unaddressable containments
> are an issue...) The only weak argument I can raise about the RDF
> approach as yet is the following: a) The set of names is infinite. b)
> The set of URIs (as a subset of names) is smaller but also infinite.
> c) The set of resolvable URIs is likely to remain countably finite. d)
> Therefore, given finite time and processing power isn't it better to
> have someway of distinguishing the set of resolvable addresses in
> advance? Problem: How do you know that a URI is resolvable in advance?
> Answer: Indicate that it should be. It will at least provide some
> help.
>=20
> I've many pages of spec to go yet though, so maybe there's something
> covering that later on(?).
Thought so. There's an interesting paragraph in Section 1.4 of the=20
RDF Semantics WD. To quote:

"If the vocabulary of an RDF graph contains URI references that are=20
not in the vocabulary [[PPJ ed. note: think that should be 'set of=20
resources' or 'universe']] of an interpretation I - that is, if I=20
simply does not give a semantic value to some name that is used in=20
the graph - then these truth conditions will always yield the value=20
false for some triple in the graph, and hence for the graph itself.=20
Turned around, this means that any assertion of a graph implicitly=20
asserts that all the names in the graph actually refer to something=20
in the world. ..."

So beware of just making up URIs that don't resolve to anything.

>=20
> --=20
> Peter
>=20
>=20
>=20
> _______________________________________________
> topicmapmail mailing list
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>=20


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