W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > April 2002

Re: Unasserted triples, Contexts and things that go bump in the night.

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Thu, 4 Apr 2002 13:40:49 -0600
Message-Id: <p05101521b8d25b743cfd@[65.217.30.94]>
To: "Jonathan Borden" <jonathan@openhealth.org>
Cc: w3c-rdfcore-wg@w3.org, www-webont-wg@w3.org
>Jeremy Carroll wrote:
>
>>
>>  As I understand it, the minimal unasserted triple proposal is that at
>least
>>  for daml:collection it would have been better if the triples with
>properties
>>  daml:first and daml:rest (and maybe those ending rdf:type daml:List ),
>were
>>  somehow special.
>
>To me the minimal proposal is to acknowledge that "dark triples" can be
>syntactically identified, and have a status in the MT.

Right, exactly.

>  >
>>  There is an intended syntactic restriction on these triples i.e. that each
>>  cell in a daml:collection has:
>>  - rdf:type daml:List (and no other)
>>  - exactly one daml:first property (pointing to a resource)
>>  - exactly one daml:rest property ( pointing to daml:nil or another cell )
>>  - no other properties.
>
>There are two perhaps at least partially, perhaps completely orthogonal
>issues:
>
>1) recursive, closed, ordered syntax of daml:List
>
>2) unasserted triples.

I agree these are both needed and are orthogonal.

>  >
>>  My point being that using dark triples to construct purely syntactic
>>  substructures within RDF graphs then begs the question of how to describe
>>  the syntax of those syntactic substructures.
>
>Right, so (1) above describes a list, and (2) describes how the list is
>interpreted (or something to that effect)
>
>  >
>>  The various schema proposals appear to me to be a way of (indirectly)
>>  constraining the syntax, and hence there is a win in terms of learning
>curve
>>  if we don't need to duplicate at the metameta level what we are already
>>  doing at the meta level.
>>
>>  I am deliberatly sidestepping whether we want daml:collection to become
>>  owl:collection.
>>
>
>There are several issues, perhaps "daml:collection" is not the best name,
>because it is a macro like parse type, which is applied to the object of a
>property, rather than a collection _class_ e.g. (using Qnames for URIrefs)
>
><daml:Property rdf:about="daml:oneOf">
>         <rdfs:range rdf:resource="daml:List"/>
></daml:Property>
>
>I have suggested that one can define two base properties "owl:set" and
>"owl:sequence"

Why do we need the set construction? I would suggest that OWL sticks 
to sequences, and omits all talk of bags, sets and other more 
complicated entities. All RDF containers are really sequences under 
the hood in any case; linearly ordered entities are what almost all 
syntax specifications require, are easy to manipulate and specify 
(they fit naturally with iteration and recursion), and have clear, 
unambiguous inferences (contrast with the muddle over rdf:Bag, for 
example.)

Pat
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Received on Thursday, 4 April 2002 14:40:49 EST

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