Datatype Disjointness

The following is a summary of the background to the OWL Working Group's decision on the disjointness of numeric datatypes. It was prepared by Ian Horrocks (OWL Working Group co-chair) on the 30th May, 2009.

The WG had initially decided not to make numeric datatypes disjoint. However, after receiving two adverse LC comments ([1], [2]) and negative feedback from implementers the WG decided to reconsider the issue. There was an extensive discussion at the F2F on 23 February 2009. Many members of the WG expressed the opinion that the above mentioned comments and feedback, as well as the benefits of compatibility with XSD, RIF and existing implementations (such as Jena and Pellet), were very strong arguments in favour of disjointness. Some WG members wanted to consult with their organisations, so a vote on the issue was postponed. At the 11 March 2009 teleconf the WG again discussed the issue, and the opinion in favour of disjointness was overwhelming; it was resolved (12 for and 1 against) to make all base datatypes, including owl:real, xsd:float and xsd:double, disjoint as per XSD.