- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Fri, 08 Mar 2002 18:49:04 +0200
- To: RDF Core <w3c-rdfcore-wg@w3.org>
- Message-ID: <B8AEB821.10594%patrick.stickler@nokia.com>
Here's my very short list of outstanding issues that I see as still remaining to be resolved for the stake-in-the-ground datatyping proposal, with proposed resolutions: 1. Union versus non-union interpretation of datatypes Overview of Issue: a) XML Schema associates a single URI with a datatype. That URI denotes the entire datatype, not just its value space. Stating that the URI only denotes the value space may be considered contrary to the XML Schema usage and leaves datatypes without a formally defined URI denoting the entire datatype. b) The present proposal does not provide any means of using rdfs:range to constrain the values of datatyped properties without resulting in the inability to use both global or local idioms freely and without conflict. c) The semantics of rdfs:drange embodies a union interpretation of datatypes by constraining a property's values to either a member of the lexical space or a member of the value space. Proposed Resolution: a) Datatype URIs denote the entire datatype, meaning the union of both lexical and value spaces. Members of both lexical and value spaces are all equal members of the RDFS datatype class. b) Use rdfs:range to associate datatypes with property values, and also constrain property values to members of the datatype class (i.e. to members of either the lexical or value space). This removes the need for rdfs:drange, providing a complete datatyping solution with no new vocabulary whatsoever. This allows for rdfs:range constraints to be defined for datatype classes without any conflict between idioms. This leaves the semantics of rdfs:range unchanged. And applications need not specially provide for the semantics of an additional rdfs:drange constraint property. I.e. the solution requires no change to existing RDFS capable systems and works fully with all existing RDFS capable systems. Since rdfs:drange already embodies a union interpretation, this is not so much a change to the stake-in-the-ground proposal as a distillation to its essential functionality. c) RDF graph syntax provides all that is needed to differentiate between members of lexical and value spaces. Literal nodes which are members of a datatype class are always interpreted to be lexical forms, the things at the blunt end of a datatype mapping. There is no loss of precision in knowing which graph nodes are lexical forms or values; yet usage is simpler and more intuitive for less technical users and consistent with clearly communicated expectations regarding the use of the inline idiom and rdfs:range for datatyping. Attached is some N3 which illustrates the proposed resolution (slightly expanded/refined from the version distributed at the f2f). Regards, Patrick -- Patrick Stickler Phone: +358 50 483 9453 Senior Research Scientist Fax: +358 7180 35409 Nokia Research Center Email: patrick.stickler@nokia.com
Attachments
- application/octet-stream attachment: rdfdt.n3
Received on Friday, 8 March 2002 11:47:17 UTC