Comment on Last Call Working Draft of RDF Semantics document concerning datatypes

I believe that there is a missing part of datatypes in the RDF model
theory, and, moreover, that this missing part makes datatypes unusable
in RDF.  The missing part is a mechanism for tieing a URI reference to
a datatype.

For example, suppose that I want to have a datatype that takes octal
numerals to the appropriate integer.  According to Section 3.4, I
create a datatype whose lexical space is octal numerals, those value
space is the integers, and whose lexical-to-value mapping is the
appropriate one.  Suppose further that I only want this one datatype.
I then form the set containing only this datatype (and some other
domain element for XML Literals).  Let's call my datatype O and the
datatype for XML Literals X, so I need to form the set { O,X } .