From: Frank van Harmelen ([email protected])
Date: 02/07/01
Below is my weekly summary of the "datatypes debate" :-) (Purpose of writing this is to check if I still understand the issues, and if so, move them forward a bit again). [a] we speak about "predefined classes" and "user-defined classes" [b] There seems to be agreement on a layered approach, as described in my earlier email (see quote [1] below) The main remaining complaints about the proposal from Ian and Peter (at http://www.cs.man.ac.uk/~horrocks/daml+oil/Datatypes) seems to be the following two points: [c] the syntax of how to actually include in DAML references to XML-Schema datatypes and their instances is unclear (apparently the examples in http://www.cs.man.ac.uk/~horrocks/daml+oil/Datatypes/daml+oil+concrete-ex.daml break RDF) Presumably, [c] should be fixable (I can't see a really deep issue here?) [d] the proposal relies on software that must be able to process in principle all of XML-Schema, which is unlikely to appear soon. A proposal to fix [d] is to redo the "easy part" of the XML-Schema datatypes (which seem to be the only parts we need) in DAML+OIL vocabulary. Advantage: no reliance on XML Schema software, disadvantage: duplication of effort between two standards. Is this anywhere near the mark? Frank. ---- [1] Quote from my earlier email (slightly revised): > in the definition of DAM+OIL+types it should be made clear that it is really > - a language with two variants, both of which are legal, > - one which allows mixing of predefined and user-defined types, using > predefined types as domains of properties etc., the other one doesn't. > - one of which is a sublanguage of the other > - where only the sublanguage is computationally tractable > - both of which can/should be given a formal semantics > - and for any set of expressions it is easy to determine to which variant > it belongs. > We then have a nice layering of languages as follows: > > RDF Schema < DAML+OIL < DAML+OIL+types[separated] < DAM+OIL+types[mixed]
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