[sc34wg3] TM Data Model issue: prop-subj-address-values

Geir Ove Grønmo sc34wg3@isotopicmaps.org
31 Oct 2003 09:40:54 +0100

* Kal Ahmed
| On Thu, 2003-10-30 at 21:54, Geir Ove Grønmo wrote:
| > I _might_ consider http://example.org/, http://example.org/.,
| > http://example.org/foobar/../, http://example.org/nodes.py?id=root,
| > http://example.org/index.htm, http://example.org/index.jsp and
| > http://example.org/index.html all to reference the same resource even
| > though they are different locators. Not sure, but this issue may boil
| > down to whether or not the same _resource_ can be referenced by more
| > than _one_ URI. This depends on our definition of what a _resource_
| > is.
| I think that is the key point. The definition of resource is not a
| clear-cut thing (not even the relevant RFCs, standards, and TAG
| pronouncements seem to match on this). Also there is the issue of what
| is a URI - are two URIs equivalent if the resolve to the same resource?
| And then you get into a circular trap...

I found the following message, which should be of interest in this


RFC 2396 (URIs) does seem to indicate that different URIs can reference
the same resource. 

| > | If you were to allow multiple subject locators, you would not only
| > | allow the arguably correct case of two locators which return the same
| > | resource, but also a whole raft of incorrect cases where the two
| > | locators return different resources. [subject locator] is the lesser
| > | of these two evils.
| > 
| > If it is incorrect -- then it is the _authors_ fault. No more no
| > less. If it is incorrect - that's a human being's fault. Shit in - shit
| > out etc. That's life.
| No, consider mirrored sites - site A is mirrored by site B, such that
| each URL x on A is mirrored to URL x' on B. Most of the time a URL x'
| resolves to exactly the same sequence of content bytes as URL x. But
| when the resource at x is updated, there is a lag before x' is
| synchronised again. So a topic with x and x' as subject indicators
| sometimes represents one resource and sometimes represents two
| resources.

Is inter-site mirroring any different from intra-site mirroring? ;)

| > Why would we not want to trust topic maps authors?
| Its not a question of trust, its a question of the model that we have for 
| URIs, resources and subjects and the particular set of heuristics that we
| choose. I feel that the original heuristics encoded in XTM 1.0 are right - 
| one locator, one resource, one subject.

I see this as a matter of whether we should let authors express the fact
that a subject, that is an information resource, can have more than a
single locator (e.g. URI) referencing it or if we should force the topic
map processor to choke if it so happened that two different authors were
using synonymous locators. I have difficulties seeing the usefulness of

Geir O.