Re: Tentative contribution to the "URI issue"

Michael Kifer wrote:

> The question is how does one differentiate URIs from strings.
> Are they strings? Should they be? If all we (collectively) want
> is to write "http://jos@debrujin.com/salary"("2020-11-22", "E100000")
> where "..." are strings, then there is no problem.
> But I don't think think this is what we collectively had in mind.
> I believe we wanted to distinguish URIs from strings and other types of
> constants.

Distinguishing symbolic constants identified by a URI from literal 
constants such as strings and integers still seems like a syntax issue 
addressable at that level in the way proposed earlier.

The conceptual proposal is that we *only* have symbolic constants 
identified by a URI and literal constants (strings, integers etc) and 
only the former are allowed to have boolean and arrow sorts.

> There is also an issue of signatures when we will start allowing or
> disallowing certain individuals to play roles of predicates, functions,
> etc.  We cannot assign a signature to any given constant, so sorts could be
> one of the grouping mechanisms here. For instance, if a dialect (like, say,
> WSML) allows only URIs to be concepts then only the constants of the sort
> rif:uri will have Boolean signatures.

What I was asking for in the meeting and my earlier message was what's 
the use case where we would allow something *other* than symbolic 
constants identified by a URI to be used as concepts?  The point being 
that I'm not convinced there is one.


I can see the value in having those symbolic constants be sorted but 
they would still be identified by URIs. [*]

In which case perhaps all we are asking is "what's the name for the top 
sort?".

If so then in RDF terms that is rdfs:Resource - everything in your 
domain is an rdfs:Resource including literals, people, unicorns and web 
information resources.

If you want a sort which is disjoint from literals (strings, integers 
etc) then from an OWL/DL point of view that would be owl:Thing.

Dave


[*] Indeed in a sorted semantic web compatible dialect then one might 
identify RIF sorts with RDF Classes so in that dialect you could say 
things like:

   all symbols of rdf:type owl:DatatypeProperty have a RIF boolean
   signature:
      OWL:Thing * rdfs:Literal

but you could also then have application-specific sorts defined using 
RDFS/OWL ontologies.

Received on Wednesday, 21 March 2007 11:11:13 UTC