Re: draft RDF datatyping response

From: Ian Horrocks (
Date: 01/08/02

On January 8, Mike Dean writes:
> This is a draft response from the Joint Committee to the RDF
> Core Working Group regarding datatyping.  We can discuss
> this during the Jan 8 telecon.
> One of the dimensions by which one can categorize datatyping
> proposals is by whether individual values are explicitly or
> implicitly typed, e.g. whether each occurrence needs to
> specify xsd:integer (explicit) or whether xsd:integer is
> specified as the rdfs:range of the property (implicit).
> We believe that RDF should allow users to choose either
> approach, and have adopted this approach in DAML+OIL.
> Allowing the user to specify rdfs:range (with or without an
> explicit value type) allows for validation; allowing the
> user to specify both allows for consistency checking;

I would NOT say this as it encourages a common misconception - that
range and domaind constraints are/can be used for "validation" (in the
sense of checking for "incorrect" data). Like any other part of the
DAML+OIL language, range and domain constraints are simply treated as
axioms, and lead to "inference" rather than validation. I.e., if you
set the range of P to be integer and add a triple <x P y>, then you
can infer that y is an integer. Of course this inference may or may
not lead to an inconsistency (e.g., depending on whether or not you
can also infer a conflicting type/value for y).

Regards, Ian

> not
> requiring an explicit value type promotes consistency with
> current use of XML DTDs and XML Schema.  We encourage the
> RDF Core Working Group to also allow both explicit and/or
> implicit typing, and believe this approach to be compatible
> with several of the current datatyping proposals.
> 	Mike

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