RE: Cutting the Patrician datatype knot

Date: 12/07/01

> >I don't see how this follows.  The value space of the XML 
> Schema datatype
> >[integer union string] is precisely the union of the value spaces of
> >integer and string.
> Yes, Ive come to see that. I simply did not conceive that anything 
> could be this badly defined. This aspect of XML datatypes really is a 
> crock. It *defines* the domain and range of the datatyping functions 
> so that they cannot possibly be the real domains and ranges. What a 
> bloody silly thing to do, I'm amazed that Thompson put his name on it.
> So, my argument does not hold if we are obliged to conform to XML 
> datatyping rules. I am inclined to just give up and leave this 
> decision to others, at this point. There is no point trying to be 
> rational when one is obliged by mandate to conform to irrationality. 
> Let me know what y'all decide.

Well, it depends on to what extent, if at all, the actual mapping
between lexical space and value space is to be described/modeled by 

My proposal is that all RDF concern itself with is 

1. how the pairing of lexical form to data type is defined (the
   definition of the pairing and the official idioms for defining
   such pairings)

2. how relations between types are defined insofar as value and
   lexical space compatability (see my recent post to rdf-interest
   proposing rdfs:subClassOf and the new rdfs:subTypeOf to handle

This approach has no problem with the XML Schema union issue. 

The mapping to an actual value that a given pairing denotes 
is performed by an application that "knows about" that data
type. If folks want to define freaky data types such as a union
of strings and integers, fine. RDF does its part by allowing one
to define the pairing of a literal (lexical form) to such a 
freaky data type, and if that works for the application, RDF is
happy for it. But RDF doesn't have to worry about the gory details
of any particular data type and the details of the particular
mapping. It only is concerned with pairings of lexical forms and 
data types -- and that pairing is what denotes the value... whatever 
it may be.

Likewise, one can define the relations between data types without
having to explicitly model the mapping between lexical and value
spaces itself or provide a canonical representation for actual

So whether XML Schema union types are a problem or not depends
on how "clever" you want RDF data typing to be. I propose the
not-so-clever approach outlined above, which captures the
essentials but leaves the bulk of interpretation to the 



Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email:

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