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Re: Should rdf:value have a semantics??

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 4 Dec 2002 14:14:25 -0600
Message-Id: <p05111b33ba140d60acd5@[10.0.100.247]>
To: "Patrick Stickler" <patrick.stickler@nokia.com>
Cc: w3c-rdfcore-wg@w3.org

Heres a rewrite of the section which hopefully will overcome the 
objections. Feel free to suggest modifications (including, delete it 
altogether :-)

Pat
----------
The intended use for rdf:value is to indicate that some entity is 
associated with a particular value, usually indicated by a literal, 
from some predefined range of possible values. Examples of this kind 
of use are given in [RDF-PRIMER]. It can used, for example, to 
associate some quantity with a literal representing the 'amount' of 
the quantity, such as a weight in kilograms or a length in yards; 
associating a textual object with a Dewey Decimal code; or for 
indicating a part or model number in some contextual range. In all 
these cases the subject of the triple will typically be a blank node 
denoting the quantity or object in question, and whose other 
properties indicate the context in which the value is to be 
understood. For example:

<ex:thing> <ex:weight> _:x .
_:x rdf:value "12.36"^^xsd:float .
_:x <ex:weightUnit> <ex:kilogram> .

<ex:doc> <dc:subject> _:x .
_:x rdf:value "020-Library Science" .
_:x <ex:classification> "DeweyDecimalCode" .

<ex:thing> <ex:assembly> _:x .
_:x rdf:value "1234" .
_:x <ex:scope> "Model2001-super"

Since the subject of the relevant triple can be any quantity, and the 
object can either be a plain literal indicating a textual 
representation of the amount or a typed literal denoting the 
numerical value of the amount, there is no way to give a formal 
specification of this intended usage.

Users are cautioned that any such usage will be context-dependent and 
is liable to be misunderstood if removed from its context. A single 
triple involving rdf:value has no particular meaning in isolation. 
The use of rdf:value in this way can often be replaced by the use of 
more complex RDF constructions or more explicit user-defined 
vocabulary in order to avoid such ambiguities.

-----

Also at the end of 4.3 (datatype entailments: informative) Ive added 
this, but it can be deleted if people think it doesnt belong (I've 
already had queries as to why this form wasnt mentioned in the MT, 
though.)

------
The informal meaning for rdf:value outlined in section 2.3.4 suggests 
the following equivalence, which we mention here for completeness as 
it represents a style of existing usage. We emphasize however that it 
is not strictly valid since rdf:value has no formal semantics, and 
that in any case the three-triple graph below does not have exactly 
the same meaning as the first triple since it does not uniquely 
associate the plain literal with the datatype:

aaa ppp "sss"^^ddd .

<-->

aaa ppp _:x .
_:x rdf:value "sss" .
_:x rdf:type ddd .

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Received on Wednesday, 4 December 2002 15:14:06 EST

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