Re: Linkbases, Topic Maps, and RDF Knowledge Bases -- help me

["Thomas B. Passin" <tpassin@home.com>]

Uchi wrote (but why single him out in this thread?) -


> *My own opinion* is that RDF, XLink and Topic maps are all complementary,
> but that XTM tends to overlap with all of them, and might just be otiose
> (or might be the perfect intersection of the three, depending on your
> opinion).

I don't really see this so-called lower-level for RDF, higher level for
Topic Maps.  They may be ***used*** that way by convention, but that's a
different matter.  I see Xlink more as infrastructure that's useful for
either (potentially, at least), just as Hytime is infrastucture that can
support ISO-flavor topic maps.

Look at the kinds of things you probably want to do wth these systems:

- Assign properties
    RDF: made for it, duck soup.
    TM: Just as simple with ISO TMs using facets.  For some reason I have
never understood, facets were removed in XTM, so now you have to assign
properties using appropriate relationships.  Quite doable, but more clumsy.

- Make assertions about objects (or resources or ...)
   RDF: Very feasible, although you may have to do some reification.
   TM: easy with built-in associations.

- Create associations
   RDF: very doable, but there is no native construct for assocations per
se.
   TM: made for it, duck soup.

- Create or use type hierarchies.
   RDF: built-in machinery.
   TM: almost built-in machinery.  You have to roll your own, but the
constructs are there.

- Create or use class hierarchies
   RDF: similar to hierarchies in constructs.
   TM: Same as for hierarchies.

- Declare that one thing is an instance of type.
   RDF: Very feasible
   TM: built-in, duck soup

- Inferencing:
   RDF: feasible but must be layered on top of RDF (as it is now).
   TM: feasible but must be layered on top, primarily no doubt by defining
the nature of various association topics.  May become built-in in the
future.

- Constructs for various container structures.
   RDF: strong
   TM: weaker, only has the equivalent of bags.

- Filter.
   RDF: no particular built-in machinery.
   TM: built-in, elaborate machinery (scopes)

- Merge maps or documents.
   RDF: conceivable but no particular provisions.
   TM: strong built-in machinery (once the XML folks get through arguing
about the ins and outs of it).

-  Easy to read fragments.  Of course this is a matter of taste to some
degree.  For me, TMs are easier to read than RDF.

So both RDF and TM have strengths and weaknesses.  But I really don't see
the high-level vs low-level thing at all.

Good Grief, I come home from work and what do I find?  500 messages about
Topic maps and RDF!  Amazing.

Cheers,

Tom P