RE: XML Schema WG comments on RDF documents

At 1:56 PM +0200 4/28/03, Jeremy Carroll wrote:

>In other words, for a union datatype, the lexical-to-value mapping is not a
>function but a relation?
>
>(You seem to be talking about the union of a number of lexical mapping
>functions; this union then ceases to be functional).

>The XML Schema WG comment questioned the "including zero", but what I hear
>now is that also the "exactly one" is incorrect i.e. for XML Schema
>Datatypes we would have:
>
>***
>A datatype mapping is a set of pairs whose first element belongs to the
>lexical space of the datatype, and the second element belongs to the value
>space of the datatype:
>
>+ Each member of the lexical space is paired with (maps to) one or more
>members of the value space.
>+ Each member of the value space may be paired with one or more members of
>the lexical space (lexical representations for that value).
>***

Close.  In fact, we don't care about "the" lexical mapping of a union
datatype.  So we don't think about the union of the various member
datatypes' lexical mappings.  It's true that that union may not be
a (single-valued) function.  What we do care about is whichever member
datatype is determined to be "operant", and then we care about *that*
datatype's lexical mapping, which *is* a function.
-- 
Dave Peterson
SGMLWorks!, for IDEAlliance

davep@iit.edu