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Re: regarding rdfms-identity-anon-resources

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Sat, 10 Mar 2001 17:54:24 +0000
Message-ID: <3AAA6A50.A3C7FE38@hplb.hpl.hp.com>
To: Jonathan Borden <jborden@mediaone.net>
CC: www-rdf-comments@w3.org
Jonathan,

Thank you for the clarification.

I have added a reference to your suggestion under the 'Further
Discussion' heading to:

http://www.w3.org/2000/03/rdf-tracking/Overview.html#rdfms-identity-anon-resources

This will appear on the W3C site in due course.

Brian


Jonathan Borden wrote:
> 
> Brian McBride wrote:
> >
> >
> > Jonathan,
> >
> > I'm not sure exactly what it is you are suggesting.  Can you provide
> > some
> > concrete examples of the application of this suggestion, outlining the
> > benefits that it brings.
> >
> > I have some more abstract questions that I'm wary of as abstract
> > discussions
> > on this topic don't always seem to clarify my understanding.  However,
> > they might give you some idea of what it is I'm not understanding.
> 
> In general my position is that the issues of naming and addressing often get
> conflated when assigning a URI to a 'resource'.
> 
> I am going to resist the temptation to answer these questions because I've
> seen these abstract discussions go round and round without apparent
> resolution. In general whether something is abstract or concrete,
> theoretical or physical depends on how you look at it and is ultimately a
> matter of local convention.
> 
> Let's start with these definitions and see how far we get:
> 
> When parsing an XML document, for the moment an XML document that conforms
> to the RDF syntax, a series of triples (p,s,o) are emitted. This set of
> triples is incorporated into an RDF model, or abstract syntax. For each
> (p,s,o) the RDF M&S 1.0 recommendation specifies a set of rules for
> generating URI references from the document being parsed.
> 
> It may occur that the syntax provides no explicit 'name' for a resource.
> Such a resource is termed 'anonymous'. The parser must assign a name to the
> resource for the purpose of generating a URI ('Skolemize'). Such functions
> e.g. generate-id() produce names such as: "genid12345".
> 
> It has been pointed out (TimBL) that such naming of anonymous resources has
> problems.
> 
> I propose that instead of 'naming' such anonymous resources, the resource
> can be addressed by its position in the originating document hence producing
> a URI reference that is an address but not a proper name.
> 
> The XPointer 'child sequence' syntax provides such addresses _with the
> benefit that syntax of these addresses does not clash with the symbol space
> of proper names_ i.e. a child sequence is of the form:
> 
> /1/2/3/4 and this can _always_ be disambiguated from an XPointer 'raw name'
> such as might be produced by an rdf:ID label (actually only if rdf:ID were a
> proper ID).
> 
> Examples:
> 
>         A name: "Fred Jones"
>         An address of an anonymous person "The man third from the left in the first
> row of the photo"
> 
> <person rdf:ID="ABC123" rdf:parseType="Resource">
>         <person.name>
>                 <first>John</first>
>                 <last>Doe</last>
>         <person.name>
>         <ssn>12345</ssn>
> </person>
> 
> the node corresponding to the element "person.name" will be 'anonymous'. It
> can be referred to with the child seq:
> 
> /1/2
> 
> it can also be referred to using the xpath
> 
> person[@rdf:ID='ABC123']/person.name
> 
> which combines a name and an address but the child seq form is a 'pure'
> address.
> 
> >
> >   o does this suggestion work when the variable is represented in N3 and
> >     there is no XML representation for it?
> 
> A proper ENBF syntax or property set for N3 would enable an addressing
> scheme for N3 documents. To my knowledge no such addressing syntax has been
> defined for N3 as yet (one can always punt and refer to the 'statement
> beginning at character 45 in the document', third statement in the document
> etc. choose. )
> 
> >
> >   o are you suggesting that any resource identified by an XPointer is an
> >     anonymous resource?
> 
> no. XPointer defines several forms:
> 
> raw name: this directly corresponds to an ID and is hence a name
> child sequence: this is an address
> combined raw name/child sequence
> full xpointer
> 
> what I am saying is that a child sequence -- which is identified by the
> starting '/' _is_ always an address and hence corresponds to an anonymous
> resource. One can identify a URI as denoting an anonymous resource by
> detecting a '/' immediately following the '#' -- i.e. in the first character
> of the fragment identifier. This is not to say that _only_ child seqs
> identify anonymous resources.
> 
> >
> > Brian
> >
> >
> > Jonathan Borden wrote:
> > >
> > > Regarding anon resources. At the RDF IG F2F I made the point
> > that one can
> > > use XPointers to identify 'anonymous' resources using three forms (of
> > > XPointer)
> > >
> > > 1) raw name - ID
> > > 2) child sequence e.g. /1/2/3
> > > 3) full xpointer e.g. #xpointer(//xxx:foo[@name='bar'])
> > >
> > > TimBL noted that it is useful to know when a resource is anonymous. I
> > > pointed out that assuming child seqs or full xpointers are used that the
> > > lexical space of a URI reference naming anonymous resource is
> > distinct (e.g.
> > > test for '/' or 'xpointer(' immediately following '#'. Hence it will be
> > > known that the URI is an 'address' not a 'name'.
> > >
> 
> Jonathan Borden
> The Open Healthcare Group
> http://www.openhealth.org
> >
Received on Saturday, 10 March 2001 12:53:27 GMT

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