[topicmapmail] multiple Source Locators

[Jan Algermissen]

Lars Marius Garshol wrote:

> | (To add to the confusion: I personally have dropped the use of
> | subject locators alltogether in projects that use Topic Maps and
> | HTTP and instead only use subject indicators. This creatly improves
> | interoperability with the technology (browsers) and also with RDF.)
> 
> I suppose it does improve interoperability with RDF, but whether
> that's an argument is very much disputable. I guess you could argue
> that dropping the use of scope and n-ary associations would achieve
> the same thing, which would of course be true, but now you'd have
> given up many of the benefits of topic maps and might as well just use
> RDF...

Just to make my point clear, what I intended to emphasize was the possibilities
of improved interoperability of Topic Maps with Web architecture, not so
much with the RDF graph.

The interoperability issues with RDF that I had in mind relate more to
the issue of using the same unique addressing context that RDF (naturally,
because it has been *designed* for the Web) uses.

BTW....
Speaking of the benefits of Topic Maps over RDF, I see basically two:

- Topic Maps are capable of representing the fact that several URIs
  refer to the same resource at the level of the abstract information
  structure, while with RDF, you need to make use of additional semantcis
  (owl:sameAs) which propagates all the way up into the queries written
  in your applications.

- RDF's statement reification mechanism does not 'induce' subject identity,
  meaning that two nodes that are the origin of the same combination 
  rdf:Subject, rdf:Property and rdf:Object (that represent semantically
  the same statement) will not merge and are explicitly not intended to merge.
  See [1] and [2] on this.


IMHO, while RDF seems to (at least partly) have been intended as a data
integration technology, there are quite some obstacles when querying
an RDF graph that is the result of merging several other graphs with
slightly differing semantics. Topic Maps provide a far more elegant
mechanism I found.

(Actually, I discovered this just when I was very close to turning to using
RDF for data integration projects that make heavy use of Web architecture,
because I could not really articulate/prove the benefit TMs provide. The
above was the reason for me not to 'convert' :o)

Jan


[1] http://lists.w3.org/Archives/Public/www-rdf-interest/2004Aug/0118.html
[2] http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#Reif

> --
> Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
> GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >
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-- 
Jan Algermissen                           http://www.topicmapping.com
Consultant & Programmer	                  http://www.gooseworks.org