Weekly summary on predefined classes :-)

From: Frank van Harmelen (Frank.van.Harmelen@cs.vu.nl)
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?


[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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