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Question about rdf:value versus element content data graph repres entation

From: <Patrick.Stickler@nokia.com>
Date: Sat, 8 Sep 2001 12:58:33 +0300
Message-ID: <2BF0AD29BC31FE46B78877321144043114BFC3@trebe003.NOE.Nokia.com>
To: www-rdf-interest@w3.org


Hi,

I have a question that I'm hoping someone with more insight to
the RDF spec than I have can provide.

My (present and possibly incorrect) understanding of the difference
between the RDF XML '<myproperty>somevalue</myproperty>' and the
condensed variant '<myproperty rdf:value="somevalue"/>' is that these
are only syntactic variants defining precisely the same knowledge
and that both are simply serializations of a subgraph corresponding to 

              [X]
               |
               |
               v
         'myproperty'
               |
               |
               v
          "somevalue"

Yet, when I run such variants through various RDF parsers, I get
the above "simple" subgraph for the content data version but a totally
different subgraph for the rdf:value variant, i.e


              [X]
               |
               |
               v
          'myproperty'
               |
               |
               v
           [gen123]
               |
               |
               v
'http://www.w3.org/1999/02/22-rdf-syntax-ns#value'
               |
               |
               v
          "somevalue"

Why does the variant syntax produce the anonymous mode
in the graph? Is it really necessary to know after-the-fact
which syntactic variant was used to serialize the knowledge?

Surely this places an extra (and possibly undue) burden on
applications wishing to operate directly on RDF graphs, in
that they must then prepare for all possible "artifacts"
of syntactic variants when querying the graph. I.e. even if
a schema states that a given property value must be a literal,
they can't be sure that the object at the end of that property
arc *is* a literal -- it could very well be an anonymous node
from which they have to then deduce the literal value by
further traversal.

Is this really a "good" thing? Is it necessary for some
fundamental behavior or characteristic of RDF graph semantics
that I'm unaware of?

All comments and explanations are very welcome.

Thanks,

Patrick

--
Patrick Stickler                      Phone:  +358 3 356 0209
Senior Research Scientist             Mobile: +358 50 483 9453
Software Technology Laboratory        Fax:    +358 7180 35409
Nokia Research Center                 Video:  +358 3 356 0209 / 4227
Visiokatu 1, 33720 Tampere, Finland   Email:  patrick.stickler@nokia.com
 
 
Received on Saturday, 8 September 2001 05:58:38 GMT

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