[tm-pubsubj-comment] Re: [topicmaps-comment] referring to a topic fromoutside a TM -- PURL

[Lars Marius Garshol <larsga@garshol.priv.no>]

* Bandholtz, Thomas
| 
| See what just has been recommended by PubSubj:
| (http://www.oasis-open.org/committees/tm-pubsubj/docs/recommendations/psdoc_
| 04.htm)
| "4.4.1 - Every PS Indicator in a PS DocSet shall be identified by, and
| retrievable through an unique canonical URI.
| This canonical URI is the corresponding PS Identifier, uniquely defined in
| the PS DocSet namespace."
| Note: ***Every*** PS Indicator, not only the whole set.

* Thomas B. Passin
| 
| I'm actually against making this mandatory, although it's good
| practice to do so when possible.  Here's why:
| 
| 1) Right now, anything retrievable through such a URI must be read
| and understood by a person, there is no topic maps mechanism to let
| a processor understand the "meaning" of the PSI.  Being online does
| not seem to be an runtime requirement for processing, but rather a
| design time benefit for software and map creators. So any means by
| which a person can get the information should be ok.

I think your argument makes sense, but I don't see why you want to
explicitly allow people to make use subject indicator URIs that don't
point to the precise subject indicator text.

Also, note that if all the URIs just point to the same file they will
be taken to indicate the *same* subject, and thus cause merging...

To me it seems better to require the URI to point directly at the
text, whatever that means.

We do need to be *really* clear on one thing: the subject indicator
itself (the resource, the text, the thing humans read) is *only* for
human documentation. It has no other purpose whatsoever. When machines
do merging they use the URI (also known as the subject identifier,
precisely for that reason).
 
| 2) It prevents people from creating useful PSIs if they don't have a
| stable website.

What do you mean?
 
| 3) It would seem to invalidate previously PSIs whose web site goes
| away for some unfortunate reason, even when the copies of the
| information are available on many other web sites.

This is a tricky question. The subject identifiers would still mean
the same thing, but it would be difficult for humans to discover that
what they do mean. I think that this would be bad practice, but that
it would be impossible to disallow it.
 
| 4) If technology were to change and so the owner of a set of PSIs
| were to want to host it using some other protocol or technology,
| they would not be able to make the change, since that would break
| the existing PSIs.

They'd have to

 a) define a new set of published subject *identifiers*,

 b) publish the old published subject *indicators* at those URIs,

 c) publish a document that maps the old *identifiers* to the new
    *identifiers*, even if they all point to the same *indicators* for
    the same subjects.

That way the old and new new identifiers could interoperate.

All this published subject stuff has a far too heavy focus on the
indicators, that is, the resources. People need to remember that these
are only used by humans, and that the machines will never ever resolve
them anyway.
 
| For these reasons, I strongly suggest that it be a matter of good
| practice rather than mandate to have the PSIs be retrievable from
| their URI.

Agreed.

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
ISO SC34/WG3, OASIS GeoLang TC        <URL: http://www.garshol.priv.no >