[sc34wg3] New SAM PSIs

Murray Altheim sc34wg3@isotopicmaps.org
Wed, 12 Feb 2003 16:27:42 +0000

Steve Pepper wrote:
> The current editors' working copy of the SAM at
> http://www.isotopicmaps.org/sam/sam-model/ there is an issue
> called "locator-notation-support" (section 3.1).

First, I don't understand what a "subtype loop" is logically,
and I can't quite think what it could be, in FOL terms. Steve?

- - - -

Secondly, pardon my ignorance of the specifics of this document,
as I've not read it in great detail, nor have I been privy to
the discussions leading to it, but I did notice that the SAM
defines a new set of PSIs equivalent to those in XTM 1.0.

I wonder what utility these perform, since they're identical.
This only seems to add confusion and potential ambiguity, in that
absent a topic map establishing these identities, implementors must
now check a PSI against two sets now, not one (this would be
hard-wired into any topic map engine). If there's no additional
functionality, these new PSIs seem superfluous and unnecessary.
We already have two URLs for each (the PSI from the core.xtm
topic map and the ID link inside XTM spec), so this makes three.

Also, I realize that the W3C has gone to great trouble to confuse
the world about the syntax of URLs, but absent an HTTP server to
link the ID (eg., "type" of "http://psi.topicmaps.org/sam/1.0/#type")
with a default document name such as "index.html" (or "index.xtm"),
why was the document name left off? It would seem it leaves
implementors with little ability to even guess what is at the other
end of that URL. (Yes, I do realize PSIs can be considered as
opaque strings).

Without wishing to open a heated debate, could someone clarify
at least the reason for the new PSIs?

Thanks much,


Murray Altheim                  <http://kmi.open.ac.uk/people/murray/>
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK

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