[sc34wg3] SAM-issue term-scope-def

Martin Bryan sc34wg3@isotopicmaps.org
Tue, 25 Jun 2002 09:00:37 +0100

Lars Marius

> | A change from the 13250 definition of "a given scope is the union of
> | the subjects of the set of themes used to specify the scope" to one
> | where the intersection is used would be a mistake.
> That is just an assertion, though. Could you say *why* you think it
> would be a mistake?

I gave the reason in the following paragraph, but to reinforce it I would
state that to have XTM use intersection while ISO13250 clearly states union
suggests that the two standards are in competion. I thought the idea was to
try to align them without changing the basic concepts.

> | The use of "all of the topics in a topic map" as the definition of a
> | unconstrained scope was a clear recognition of the fact that any of
> | the currently defined topics could, at some stage, be used to scope
> | any other topic.

> That makes sense, but as Marc explained very clearly at the beginning
> of the previous thread, this solution has serious problems.

Marc's preferred option in his 7th June message is "the set of all topics",
which I agree with as it matches the wording in ISO 13250. I have not noted
any change in Marc's position since then. I, however, offered an alternative
that seemed to have been overlooked.

> | What I would suggest is that we should have said that unconstrained
> | scope was the union of all topics currently used as scopes. Yet no
> | one seems to have listed this as a possible alternative definition.
> We could do that, but it would mean that
>  a) the unconstrained scope changes every time a new theme is added to
>     a scope, and

Yes, just as it would if you added a new topic and made that the scope of
another topic. Are you saying that latter should be disallowed as well? We
have to allow for the extension of the set of scopes used within XTM, both
during merging and before/after. At merge time we have a static set of
topics, so what is the problem?

>  b) it would be subject to exactly the same problem that Marc
>     described.
> So I don't think that is a viable solution.

The problem is that the intersection of scopes approach causes loss of data,
and that I do not like. Marc's suggestion of using all topics is the correct
one, but this may result in too heavy an overload for processing. My
suggestion would provide a halfway house between the two extremes. (Not that
I expect anything I suggest to be used!)