- From: Graham Klyne <GK@Dial.pipex.com>
- Date: Mon, 01 Jan 2001 18:35:30 +0000
- To: David Megginson <david@megginson.com>
- Cc: "RDF interest group" <www-rdf-interest@w3.org>
At 07:33 AM 12/30/00 -0500, David Megginson wrote: >Bill de hÓra writes: > > > Jonas is right but not only for that reason. The RDF numeral > > identifier scheme doesn't come with the everyday semantics people > > associate with numbers, specifically numeric ordering. They are > > just tokens that happen to be confusing to the human reader. Seq > > does require ordering though. I like to see this sceheme dropped, > > it seems to bend the readability req of XML (it's very readable but > > very confusing), but what would replace it? > >There are two alternatives: > >1. revise the spec to declare that RDF statements are ordered to begin > with (i.e. a processor that reads an RDF document preserves the > relative order of all statements for any given resource); or Ouch! I think that is not possible with RDF graph-syntax. If there is ordering, I think it needs to be stated explicitly in the graph. >2. use resources for property values and add positional information, i.e. > > <foo:Person rdf:about="urn:xxx:0001"> > <dc:title>Joe Smith</dc:title> > <foo:job-history rdf:parseType="Resource"> > <foo:job-item dc:title="Intern" foo:pos="1"/> > <foo:job-item dc:title="Sales Rep" foo:pos="2"/> > <foo:job-item dc:title="Sales Regional Manager" foo:pos="3"/> > <foo:job-item dc:title="Booth Babe" foo:pos="4"/> > <foo:job-item dc:title="VP Sales" foo:pos="5"/> > </foo:job-history> > </foo:Person> > >(I wrote the above example in heavily-abbreviated RDF syntax, and will >leave it as an exercise for the masochistic reader to write it out in >fully unabbreviated RDF syntax.) That's a possible approach (though I think it has some of the disadvantages of the present mechanism -- how do I add something between "Intern" and "Sales Rep"?). Actually, I think that there are an arbitrary number of ways that ordering information can be captured in a graph, and it's not clear to me that any one is best for all possible uses. E.g. in CC/PP, we are proposing a graph structure with "nextXXX" properties to indicate the sequence of proxy-derived capability modifications. This effectively, builds the sequence directly in the RDF graph. I can imagine an approach in which 'precedes' and/or 'succeeds' properties are added between sequence members. Real-valued position values are another. I could go on. Given this wealth of possibilities, all possible using the existing RDF base, I don't see why explcit sequencing constructs need to be added to the fundamental RDF structure. #g ------------ Graham Klyne (GK@ACM.ORG)
Received on Monday, 1 January 2001 14:11:10 UTC