[sc34wg3] XLink in XTM

Lars Marius Garshol sc34wg3@isotopicmaps.org
24 Feb 2003 20:34:49 +0100

* Lars Marius Garshol
| I've spent some time on the new XTM syntax specification this
| evening, and realized that there are quite a few XLink-related
| issues that we have never thought through in any depth.

* Murray Altheim
| I'm not sure who "we" is, 

In the sentence above I was talking about the TM community as a whole.

| What we ended up with is what was possible, i.e., defined within the
| XLink 1.0 Recommendation. I've expressed my regrets and
| disappointments with this previously. 

I tried looking for documentation on this, but couldn't find any. If
you have references they are much appreciated.
| If you look again you'll see that the XTM 1.0 DTD has a FIXED
| attribute for "simple" already.

My mistake; I'm sorry. I thought only <mergeMap> had it, but I see now
that that's a mistake I made in copying to the new syntax spec, and
that XTM 1.0 has this for every element that has xlink:href. Sorry.
Let's forget that one.

| [xtm-xlink-actuate]
| I believe we went through this in some detail during the development
| of XTM, and we didn't include this because none of the definitions
| for the 'actuate' attribute make any sense for XTM; 'actuate' is all
| about presentation, and XTM documents aren't presented, they're
| processed. Also, link traversal varies in XTM in different contexts.
| 'actuate' was designed really only for presentation of textual
| documents -- this is quite clear if you read the definitions for its
| values: "new", "embed", "replace", "other" or "none". For XTM it'd
| always have been "other" or "none".

You are confusing -actuate- with -show-. -show- has those values, and
is all about presentation, but I'm talking about -actuate-, which is
about when the link is traversed. XTM 1.0 allows the application to
choose whether or not to follow external references, but with
-xlink:actuate- topic maps could themselves express what they would
| XTM 1.0 documents are by definition valid according to the DTD. 

As defined by XTM 1.0, yes. It's not decided yet whether ISO 13250
will phrase the conformance constraints in exactly the same way. For
example, documents that don't have the DOCTYPE declaration might still
be correct XTM 1.1 (or whatever we call the new version). (In fact,
there are a number of XTM implementation that barf if presented with
an XTM document where the system identifier in the DOCTYPE points to a
missing resource.)

| BTW, these issues don't change with other schema languages, only get
| more complex and less widely supported.

Yes and no. If we use pure RELAX-NG things actually get quite a bit
simpler, since RELAX-NG does not modify the XML document in any way.

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