utype questions

[Norman Gray]

Greetings, all.

[I'm slightly late to this part of the party -- I've had some bad  
email troubles this week, and may be missing messages]



There are three issues being discussed here, which are coupled but  
distinct:

1. How are UTypes named?  Are they a dead string, some general URN, or  
an HTTP URI?

2. Supposing they are dereferenceable, what comes back when you  
dereference them?

3. Supposing what comes back include RDF/SKOS/Ontologies, which  
vocabulary/ontology should they be?

Questions (2) and (3) presuppose an earlier answer, but a discusison  
of (1) does not depend on, or imply, an answer to (2) or (3).


1: My proposal is limited to providing an answer to (1), plus some  
discussion of how UTypes are conceptualised.  The downsides of an HTTP  
URI are that it is longer than the UTypes defined in SSA (but bytes  
are cheap), and that it is not trivially compatible with current SSA  
implementations (though I have described how it could easily be made  
so in practice).  The upsides are that is very extensible to the  
problems we may face in the next couple of decades, and can be  
practically useful IF it is derefereceable.  It would not NEED to be  
dereferenceable, and I do not envisage current applications  
dereferencing anything 'live'.

2: IF a URI is dereferenceable then, as you know, it can return  
multiple things, depending on the HTTP 'Accept' request header.  It  
can return HTML and/or XML and/or RDF, ... anything.  What a URI-UType  
returns needn't be standardised yet, and though I refer to this in my  
proposal, it's not core.

3: It's important to be clear about the distinctions between  
ontologies and vocabularies.  Terms in a 'vocabulary' have rather  
loose meanings (not even necessarily as precise as Roy's  
'probabilistic'), and have a range of use cases clustering around  
_searching_.  You can't do inferencing with them, and they're not  
precise enough to use for data access.  A 'data model' is an  
'ontology'.  Data models are very important (and they are generally  
more sophisticated things than vocabularies), but I don't believe we  
have to finally settle this part of the argument yet.



I'll follow this up with a couple of more specific postings about  
these separate aspects, to try and keep these separate strands separate.

Best wishes,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
Dept Physics and Astronomy, University of Leicester, UK