[topicmaps-comment] referring to a topic from outside a TM (was:multilingual thesaurus - language, scope ,and topic naming constraint)

["Bandholtz, Thomas" <thomas.bandholtz@koeln.sema.slb.com>]

Title: [topicmaps-comment] referring to a topic from outside a TM (was: multilingual thesaurus - language, scope ,and topic naming constraint)

> From: Thomas B. Passin
[...]
> ....  Whether a
> topic is referred to by its ID directly (e.g., by a program  instantiating
> that map in memory), or by xlink:href is secondary, since the href is
> supposed to refer to the topic by its ID as in
>
> xlink:href='#thetopic'
>
> This mean the ID is treated as a URI (when you normalize it
> to include the base URI of the owning document). 

Try this with http://psi.ontopia.net/ontopia/ontopia.xtm#topicmap in IE 6.0. You will see the top (!) of Steve Pepper's XTM-document, while the topic with id="topicmap" resides two scrolls below. Is this a bug or a feature?

In any case IE 6.0 (having a rather developed XML handling - whatever you may think about microsoft :-)) does not handle an URI anchor for XML formats. What's the difference?

In HTML (not necessarily indicated by the filename's suffix), the browser positions to a (hidden) tag

<a name="topicmap">.

Do we expect the application - in an XML doc -  to position to an element with id="topicmap" ? 
(this may be any element name, in an XTM topic map at <topic id="topicmap">).

IE does not handle an anchor in an XML doc at all.

Consulting the XLink rec on xlink:href (http://www.w3.org/TR/2001/REC-xlink-20010627/#link-locators), I found something interesting:

<<<<< For locators into XML resources, the format of the fragment identifier (if any) used within the URI reference is specified by the XPointer specification [XPTR]. >>>>>

(The "fragment identifier"  into HTML resources is the anchor indicated by a leading '#' like in the above (not-working) example).

I just started to re-read XPointer (http://www.w3.org/TR/2001/WD-xptr-20010108/).  Following this spec i should have used:

 http://psi.ontopia.net/ontopia/ontopia.xtm#xpointer(id('topicmap'))

IE does ignore this anchor either. A look at http://www.w3.org/XML/Linking shows that all this is just standardized (w3-rec) but not widely implemented yet.

Anyway: I think that the syntax (HTML-style).

 http://psi.ontopia.net/ontopia/ontopia.xtm#topicmap

should be replaced by the XPointer syntax to be synchronized with the standardization process.

 As far as i have understood, this will still be a valid value for an xlink:href attribute (as it is an URI). So it conforms with the XTM DTD.

Remember there is also a third valid syntax (besides document-anchors and xpointer): a HTTP GET request like

 http://psi.ontopia.net/ontopia/ontopia?id=topicmap.

This would require not a document at all, but some server processing at  http://psi.ontopia.net/ontopia/ontopia.

(You can also specify a HTTP-GET binding for a Web Service, BTW).

Thomas Bandholtz
XML Competence Center
SchlumbergerSema
Sema GmbH
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D50679 Köln/Cologne
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