OWL unified numbers

This is a synopsis of OWL number type unification issue, which boils down to the question of whether a floating point literal 3 and an integer literal 3 are to be interpreted to be the same value or different values.

In July 2008, as a possible resolution to its issue 126, Boris Motik prepared a proposal for a treatment of numbers, based on a paper he coauthored with Ian Horrocks. The proposal made decimal and floating point both be subtypes of a real number type. At its face-to-face in July 2008, the working group felt there was consensus on the proposal, and the design was instituted, eventually reaching last call in December 2008.

Precipitated by LC comments 22 and 24, the WG revisited its design at the Feb 2009 F2F, both expressing the concern that RIF number types were disjoint and therefore incompatible with OWL. Most of the WG agreed that there was a problem, leading to a resolution soon thereafter to reverse its decision and define that number types should be disjoint. Alan registered an objection at this time as the sole no vote against this resolution.

In subsequent email Alan consulted Jos de Bruijn, a member of the RIF WG, responding to the issue of RIF incompatibility. As this hinged on the application of the XML Schema Datatypes 1.1 draft, Alan sought an opinion from its editor, Dave Peterson. Peterson's response supports the notion that XSD type disjointness does not necessarily apply to OWL.

TBD: Short summary of Alan's argument about RIF, XPath, and implementation dependence.

In addition to RIF compatibility, Boris Motik asserted that comparison of floats to integers was difficult. Alan responded with a citation to a published paper describing a technique for efficiently comparing floats to integers.