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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@[]>
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 :-)

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, 

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 UTC

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