Re: [topicmaps-comment] occurences and modeling resources

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

* Howard Goldberg
| 
| In the example of 3.9.1 of xtm 1.0 (<occurence> Element)
| 
| <topic id="hamlet">
| . . .
| 	<occurrence id="hamlet-in-xml">
| 		<instanceOf> ...</instanceOf>
| 		<resourceRef xlink= ". . .>
| 	</occurrence>
| </topic>
| 
| and the occurrence is reified by 
| 
| <topic id="hamlet-in-xml-topic">
| 	<subjectIdentity>
| 		<subjectIndicatorRef xlink:href="#hamlet-in-xml">
| 	</subjectIdentity>
| . . .

This is fine.
 
| If I create topic2 with the same occurrence as topic hamlet, are the
| occurrence id's the same in both topics, or does topic2 have a
| unique occurence id

All IDs in XML documents must be unique, so there is no other way to
do it.

| and the reified occurrence have multiple subjectIndicatorRefs?
 
Well, no, you can't do that. The problem is that these two occurrences
are two different relationships, one between 'hamlet' and the resource,
and one between 'topic2' and the resource. If you reify both with the
same topic you are implicitly saying that they are the same thing,
which is wrong.

| <topic id="topic2">
| . . .
| 	<occurrence id="hamlet-in-xml">
| 	[same elements as above] . . .
| </topic>

This isn't valid XML, since you have two equal IDs.
 
| <topic id="topic2">
| . . .
| 	<occurrence id="topic2-in-xml">
| 	[same elements as above] . . .
| </topic>

This is fine, but the topic below is not, for the reason explained
above.
 
| <topic id="hamlet-in-xml-topic">
| 	<subjectIdentity>
| 		<subjectIndicatorRef xlink:href="#hamlet-in-xml">
| 		<subjectIndicatorRef xlink:href="#topic2-in-xml">
| 	</subjectIdentity>
| . . .

There is only one way this can be OK: if 'hamlet' and 'topic2' have
the same subject. If they do then there's not really any reason to
have two different topics for it, though you could, and in that case
the two different occurrences would collapse into a single occurrence.

--Lars M.