[sc34wg3] Questions on N0396: (6) topic map item (how do I find all occurrences?)

[Lars Marius Garshol]

* Jan Algermissen
| 
| Besides the [reifier] property, all properties are NOT computed ones
| with the only exception of [roles played] on the topic item.
| 
| What is the rationale behind providing the role playings information
| as a computed property but not the others I have been talking about
| (e.g. all occurrences of a topic map item).

Frankly, I'm glad to see someone finally ask this question. I do
wonder why you seem to accept [reifier] without but question the
inclusion of [roles played].

The reason is simply that topic map gospel has held for a long time
that "topics have three kinds of characteristics: names, occurrences,
and roles played in associations". Given that it this was, in a sense,
the heart of the TAO model, it seemed too strange to leave out the
[roles played] property despite its strictly speaking being redundant.
Basically, the thinking was that the data model would then deviate too
far from the conceptual model.

It could be taken out without loss of information and without making
the model any more awkward to use for its intended purpose. 
 
| Since the properties that do not provide the 'essential connections'
| (the connections that preserve the structure of the topic map) don't
| actually have any effect (see conformance discussion), I wonder why
| THIS property is there?

All three computed properties ([reifier], [reified], and [roles
played]) are redundant.

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >