[sc34wg3] Questions on N0396: (2) one or more association memberships

Lars Marius Garshol sc34wg3@isotopicmaps.org
18 Apr 2003 17:39:50 +0200

* Jan Algermissen
| In section 3.8 it says:
| "An association is a relationship between one or more subjects."
| This implies that there can be a "relationhip between one subject".
| Could you clarify what that is allowed and what meaning an
| association with only one membership is supposed to convey?

This is a carry-over from HyTM and XTM, both of which allow unary
associations. The rationale, I've been told, was that unary
associations are essentially assertions about a single subject, such

  is-inquisitive(jan : person)

SAM has to have this because HyTM and XTM have it.

| I suggest to constrain the cardinality of the [roles] property of an
| association item to be two or more.

No can do, since that would break backwards compatibility. 

I'm pretty sure I've seen people use this in actual topic maps, though
I forget where.
| If the [role playing topic] property of the association role item
| would be optional, role players could missing while ensuring that
| associations have at least two association roles.

You can still leave it out in the syntax, but we don't really
recommend that. 

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