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rdfs:member for Collections and collection syntax?

From: Dan Connolly <connolly@w3.org>
Date: Fri, 21 Feb 2003 12:01:27 -0600
To: www-rdf-comments@w3.org
Message-id: <1045850487.478.392.camel@dirk.dm93.org>

In DAML+OIL, we had item, inferred from first/rest...

<rdf:Property rdf:ID="item">
  <rdfs:comment>
    for item(L, I) read: I is an item in L; either first(L, I)
    or item(R, I) where rest(L, R).

http://www.daml.org/2001/03/daml+oil#item
http://www.w3.org/TR/2001/NOTE-daml+oil-reference-20011218

In RDFS, member seems to have no relation to first/rest...
http://www.w3.org/TR/2003/WD-rdf-schema-20030123/#ch_member
http://www.w3.org/TR/rdf-schema/#ch_collectionvocab
http://www.w3.org/TR/2003/WD-rdf-schema-20030123/#ch_collectionvocab

I thought rdfs:member was specified ala daml:item
to be inferred from first/rest.

I did some implementation assuming those semantics...
I was given a collection of a WG's documents,
and I just wanted the documents. There's no single
property that will get me from the WG to the documents,
so I used rules to make up the difference...

------
{
  :GROUP a org:WorkingGroup; con:homePage :PG.

  :F is log:semantics of [ a :GroupKB].


  (:F { this log:forAll :L, :X.
         { :L l:first :X } log:implies { :L l:item :X }.
         { :L l:rest [ l:item :X ] } log:implies { :L l:item :X }.
       }) log:conjunction [ log:conclusion :FLists ].

  :FLists log:includes {
        [ a org:WorkingGroup;
          con:homePage :PG;
          wgi:hasDrafts [ l:item :WORK ]
        ]
  }.
}
  log:implies { :GROUP org:deliverable :WORK }.
-------

... but that seems like a big hassle when the RDF
parser could have just spit out rdfs:member triples
along with rdf:first and rdf:rest triples.

In sum...

 (1) pls specify that rdfs:member connects collections
 to their members

 (2) specify that parsers spit out rdfs:member triples
 when parsing Collection syntax.

 (3) specify that parsers spit out rdfs:member triples
 for old-style _n Containers too.

Hmm... I suppose there could be missing member triples
if the RDF/XML syntax used explicit first/rest or
explicit rdf:_n triples. But that seems acceptable
to me.

This idea is probably too late to be worth the trouble.
But it comes from real implementation experience,
and I figure I ought to report the experience,
even if the WG decides it's not worth the change
at this point.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 21 February 2003 13:01:28 GMT

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