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Differences between rdfs:Datatype vs owl:DataRange

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Tue, 27 Nov 2007 17:10:02 +0000
Message-ID: <474C4F6A.2050807@hpl.hp.com>
To: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>


Concerning ISSUE-29, and my ACTION-27:

If something is an rdfs:Datatype then it is required to

a)
http://www.w3.org/TR/rdf-schema/#ch_datatype
[[
All instances of rdfs:Datatype correspond to the RDF model of a datatype
]]

b)
http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-Datatypes
[[
A datatype consists of a lexical space, a value space and a 
lexical-to-value mapping.
]]

c)
http://www.w3.org/TR/rdf-mt/#dtype_interp
[[
A datatype is an entity characterized by a set of character strings 
called lexical forms and a mapping from that set to a set of values. 
Exactly how these sets and mappings are defined is a matter external to RDF.

Formally, a datatype d is defined by three items:

1. a non-empty set of character strings called the lexical space of d;

2. a non-empty set called the value space of d;

3. a mapping from the lexical space of d to the value space of d, called 
the lexical-to-value mapping of d.

The lexical-to-value mapping of a datatype d is written as L2V(d).

In stating the semantics we assume that interpretations are relativized 
to a particular set of datatypes each of which is identified by a URI 
reference.
]]

but note that the final URI reference is not required for a datatype.

===

On the other hand an owl:DataRange is a set of literal values, (in OWL 
1.0 only finite sets are supported).

http://www.w3.org/TR/owl-ref/#EnumeratedDatatype
(unhelpful??)

http://www.w3.org/TR/owl-semantics/rdfs.html#5.2
[[
owl:DataRange 	CEXTI(e)⊆LVI  	OWL dataranges are special kinds of datatypes.
]]
(text incorrect - well misleading, a datarange does not suggest a 
lexical-to-value mapping?)


====
My analysis is that the value space of any rdfs:Datatype is an 
owl:DataRange, because it satisfies CEXTI(e)⊆LVI, but not conversely, 
because of the lack of a lexical-to-value mapping.

If this analysis holds, then Holger's suggestion of using an (anonymous) 
rdfs:Datatype in this case may be plausible, and is more precise than 
using owl:DataRange.

Jeremy
Received on Tuesday, 27 November 2007 17:10:31 GMT

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