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RE: Problem with TDL (EVEN BIGGER ONE)

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Sat, 19 Jan 2002 12:58:56 -0000
To: "Patrick Stickler" <patrick.stickler@nokia.com>, "ext Sergey Melnik" <melnik@db.stanford.edu>
Cc: <www-archive@w3.org>
Message-ID: <JAEBJCLMIFLKLOJGMELDOEMKCCAA.jjc@hplb.hpl.hp.com>


Sergey, Patrick,

this discussion presupposes a Model Theory for TDL which Patrick has
explicitly not furnished.

Of course I am going to solve the issues with a stroke of a magic wand.

When the magic happens either be amazed and applaud or (more likely) offer
criticism at that point!

Jeremy

> -----Original Message-----
> From: Patrick Stickler [mailto:patrick.stickler@nokia.com]
> Sent: 19 January 2002 10:16
> To: ext Sergey Melnik
> Cc: www-archive@w3.org; Jeremy Carroll
> Subject: Re: Problem with TDL (EVEN BIGGER ONE)
>
>
> On 2002-01-18 22:41, "ext Sergey Melnik" <melnik@db.stanford.edu> wrote:
>
> > Patrick,
> >
> > thank you for the clarification. In fact, your approach suggests a third
> > original idiom, in which typed elements are interpreted as pairs (value,
> > lexical representation). I'm going to accommodate this idiom in the
> > datatyping document that I'm editing.
> >
> > However, under the above interpretation, your document [1] is
> > inconsistent. The figures in 3.1 and 3.2 can only be consistent with
> > each other, if literals (rectangles) are interpreted as pairs. This is
> > fine, but you run into the issue that the interpretation of literals is
> > context-sensitive (i.e. not fixed, but depends on the property that the
> > literals are handing off). So, for example, the literals hanging off
> > rdf:value are now also interpreted as some kind of pairs.
>
> I'm not sure I follow you. The idiom requires that rdf:value has
> a literal value. It is not a recursive idiom. You can't have
> an anonymous node with an rdf:value that is itself an anonymous
> node with an rdf:value....
>
> Perhaps this is not specified clearly enough in the discussion
> of the idiom. I will try to make that clearer.
>
> Note though, that this is an issue with the idiom, not the TDL
> model.
>
> The separation from the TDL model and the idioms employed is
> intentionally strict -- so that each idiom is simply a means
> of expressing a pairing, and the pairing itself is the foundation
> of interpretation.
>
> > Furthermore, your scheme *does* require modifications the the present
> > RDF graph model: it is based on untidy graphs, quite in contrast to what
> > you claim! In other words, you cannot just merge two literals with the
> > same content together (they might represent two different pairs,
> > depending on the properties they are hanging on).
>
> My understanding of graph tidying is that nodes with literal labels
> and anonymous nodes are never merged. Only nodes with URIref labels.
>
> Thus, you would never merge two literals. Every literal node (every
> instance of a lexical form) is unique in the graph.
>
> If this is not correct, then that's *major* news to me, and I'll
> have to go back and re-re-re-re-read the MT and other relevant
> discussions.
>
> Thus, per my present understanding, TDL is based on tidy graphs,
> and both of the defined idioms are valid for tidy graphs without
> the problems you indicate.
>
> Also, again, if it turns out that I am mistaken about the tidying,
> it is only an issue of the particular idiom, and not of the TDL
> model itself.
>
> Regards,
>
> Patrick
>
> > All in all, given your clarification, your scheme is a specialized
> > variant of Patel-Schneider's/Hayes' one, but with some false claims...
> >
> > Sergey
> >
> > [1] http://www-nrc.nokia.com/sw/TDL.html
> >
> >
> > Patrick Stickler wrote:
> >>
> >> On 2002-01-18 4:42, "ext Sergey Melnik" <melnik@db.stanford.edu> wrote:
> >>
> >>> Patrick,
> >>>
> >>> there is a well-known problem with the rdf:type/rdf:value
> representation
> >>> that you described in
> >>>
> >>> http://www-nrc.nokia.com/sw/TDL.html
> >>>
> >>> In essence, the interpretations of nodes _1 and _2 in
> >>>
> >>> _1 rdf:value "3.0"
> >>> _1 rdf:type us-double
> >>> _2 rdf:value "3,0"
> >>> _2 rdf:type german-double
> >>>
> >>> fall together (_1 and _2 represent the same real value), and
> the pairing
> >>> between the lexical representation and the type gets corrupted.
> >>> Specifically, the semantics of the above four statements is equivalent
> >>> to that of
> >>>
> >>> _3 rdf:value "3.0"
> >>> _3 rdf:value "3,0"
> >>> _3 rdf:type us-double
> >>> _3 rdf:type german-double
> >>>
> >>> How do you suggest to work around this problem?
> >>
> >> There is no problem.
> >>
> >> The nodes _1 and _2 would *never* be merged in that fashion.
> >>
> >> 1. They do not denote the same value space member of the same
> >> datatype as us-double is not the same datatype as german-double.
> >>
> >> 2. Neither anonymous nodes nor literal labeled nodes participate
> >> in graph tidying.
> >>
> >> The fact that the TDLs ("3.0",us-double) and ("3,0",german-double)
> >> may correlate to the equivalent member in each other's value spaces or
> >> in the value space of e.g. xsd:double is a matter
> >> of interpretation -- not of representation.
> >>
> >> E.g.
> >>
> >> <rdfl:LexicalDatatype rdf:about="xsd:double"/>
> >>
> >> <rdfl:LexicalDatatype rdf:about="us:double">
> >>    <rdfl:lexicalSubClassOf rdf:resource="xsd:double"/>
> >> </rdfl:LexicalDatatype>
> >>
> >> <rdfl:LexicalDatatype rdf:about="german:double">
> >>    <rdfs:subClassOf rdf:resource="xsd:double"/>
> >> </rdfl:LexicalDatatype>
> >>
> >> which defines, as we would expect, that the value
> >> space of both us:double and german:double are subsets
> >> of the value space of xsd:double but only the lexical
> >> space of us:double is a subset of the lexical space
> >> of xsd:double.
> >>
> >> (note the difference between rdfs:subClassOf and
> >> rdfl:lexicalSubClassOf!)
> >>
> >> And if we know that the value spaces of us:double
> >> and german:double are in fact a perfect intersection,
> >> then we can also say
> >>
> >> <rdfl:LexicalDatatype rdf:about="us:double">
> >>    <rdfs:subClassOf rdf:resource="german:double"/>
> >> </rdfl:LexicalDatatype>
> >>
> >> <rdfl:LexicalDatatype rdf:about="german:double">
> >>    <rdfs:subClassOf rdf:resource="us:double"/>
> >> </rdfl:LexicalDatatype>
> >>
> >> which says that any member of the value space of
> >> us:double is also a member of the value space of
> >> german:double and visa versa.
> >>
> >> Thus, there is no problem.
> >>
> >> The nodes in your example would never be merged, and
> >> the relationships between the lexical and value spaces
> >> of the datatypes in question are explicitly defined,
> >> and interpretation about whether the two TDLs
> >> ("3.0",us-double) and ("3,0",german-double) denote
> >> the same value happen outside the RDF-space, yet
> >> the RDF representation -- using the TDL scheme -- is
> >> fully sufficient for making that interpretation.
> >>
> >> Cheers,
> >>
> >> Patrick
> >>
> >> --
> >>
> >> Patrick Stickler              Phone: +358 50 483 9453
> >> Senior Research Scientist     Fax:   +358 7180 35409
> >> Nokia Research Center         Email: patrick.stickler@nokia.com
>
> --
>
> Patrick Stickler              Phone: +358 50 483 9453
> Senior Research Scientist     Fax:   +358 7180 35409
> Nokia Research Center         Email: patrick.stickler@nokia.com
>
>
>
Received on Monday, 21 January 2002 05:05:29 GMT

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