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Re: XLink olden days

• To: Lars Marius Garshol <larsga@g...>
• Subject: Re: XLink olden days
• From: Uche Ogbuji <uche.ogbuji@f...>
• Date: Sat, 10 Aug 2002 22:17:10 -0600
• Cc: xml-dev@l...
• In-reply-to: Message from Lars Marius Garshol <larsga@g...> of "10 Aug 2002 23:58:39 +0200." <m3ptwq74vk.fsf@p...>
• Sender: uche.ogbuji@f...

> 
> * Uche Ogbuji
> | 
> | BTW, XML Topic Maps was able to use XLink quite well.  It seems
> | their demands would be more exacting than those of a hypertext
> | presentation format.  I have long expressed support/desire for an
> | RDF serialization that uses XLink, and in the little experimentation
> | I've undertaken, I also don't see the insurmountable problems XLink
> | poses.
> 
> I think the problem here is not obstacles presented by XLink, but the
> fact that it is not clear what value XLink adds. Sure, XTM uses XLink,
> but what does that buy us? Frankly, apart from marketing value I must
> admit I have no idea. 
> 
> As far as I know, nobody has ever used the XLink mechanisms in XTM for
> anything, or even considered doing something concrete with it. I don't
> expect to ever see it, either.
> 
> XLink is weaker than it seems, since although the arcs are strongly
> typed the identity and nature of the nodes being connected is anything
> but clear. In RDF and topic maps, however, that is different; you know
> perfectly well what is being linked.
> 
> I think XLink has value for documents, but for data (like topic maps
> and RDF) I just don't see the point. For these forms of information,
> topic maps and RDF do the same thing, and they do it so much better
> that using XLink for data is pointless.

OK.  I understand this, but is it really such a problem?

XLink by itself doesn't add semantics to the node and the arcs.  I think it's 
a syntactic framework.  The idea is that any app encountering an XLink can at 
least provide the most rudimentaty behavior.  More sophisticated apps, such as 
XTM, can also supply their own semantics.  At it turns out, XLink is very well 
suited to this distinction because of its use of qualified attributes.  You 
can then use the element in which the link occurs to establish the 
higher-order semantics, which is precisely what XTM does.

In fact, the areas where I have the most quarrel with XLink are where they mix 
in a semantic level that I think inappropriate, for example the actuate stuff. 
 I think this should be left to specialized attributes in the vocabulary using 
XLink.

So in the end, I think XLink's lack of baked-in semantics makes it perfect for 
simple apps such as XHTML and more complex ones such as XTM and RDF.

I think it's useful that any XLink-aware app would be able to make some sense 
of XTM even without being a topic maps processor.  I'd like the same benefit 
for RDF.


-- 
Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Track chair, XML/Web Services One Boston: http://www.xmlconference.com/
Basic XML and RDF techniques for knowledge management, Part 7 - 
http://www-106.ibm.com/developerworks/xml/library/x-think12.html
Keeping pace with James Clark - http://www-106.ibm.com/developerworks/xml/libra
ry/x-jclark.html
Python and XML development using 4Suite, Part 3: 4RDF - 
http://www-105.ibm.com/developerworks/education.nsf/xml-onlinecourse-bytitle/8A
1EA5A2CF4621C386256BBB006F4CEC

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    • From: Lars Marius Garshol <larsga@g...>

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