[sc34wg3] Removing added scope from <mergeMap>

Geir Ove Grønmo sc34wg3@isotopicmaps.org
Mon, 16 Jan 2006 10:56:41 +0100

On 1/13/06, Steve Pepper <pepper@ontopia.net> wrote:
> * Kal Ahmed
> | ...and in the representation of a merge directive in XTM.
> Here I would like you to explain why. It was Lars Marius and
> Graham, editors and implementers, who came up with the idea that
> added scope on <mergeMap> should be done away with. It was a bit
> "last minute", so I would be interested to hear from one of their
> peers, *why* you think this might not be such a good idea.

There are two mechanisms you can use to track provenance in topic
maps. Those are scoping and item identifiers (previously known as
source locators).

Scope only gets you a little further than half-way as it only applies
to topic characteristics and not the topics themselves. So, given a
topic with no characteristics there is no way, with scope only, to
unmerge that particular topic . The only way you can know that is if
the topic has an item identifier pointing back to the source topic

With item identifiers you get exactly the same "functionality" that
added scope on <mergeMap> gives you (and more), and you get it for
free (as do the implementers).

Another thing that one should consider in this discussion is that
there are two things that one does not know the provenance of: subject
identifiers and subject locators.

Geir O.