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Response to:



The intended mechanism for datatype extension is described in SPARQL 1.0, section 11.3.1 "Operator Extensibility" [1].

An implementation may extend function evaluation and comparison by adding new rows to the dispatch table.

In your example of:

"42"^^unit:Meter > "8"^^unit:Meter

which in base SPARQL is an error (no matching operator for ">" between unit:Meter and unit:Meter), the correct extension is to add ">" for (unit:Meter , unit:Meter).

The SPARQL test suite includes tests on xsd:date (see [2]) and are marked in the test suite with mf:requires

The group feels that implicit casting of unknown datatypes to numerical types would be a less useful mechanism.

We would be grateful if you would acknowledge that your comment has been answered by sending a reply to this mailing list.

Andy (on behalf of the SPARQL WG)

[1] http://www.w3.org/TR/rdf-sparql-query/#operatorExtensibility
[2] http://www.w3.org/2001/sw/DataAccess/tests/data-r2/open-world/date-3.rq