XML schema draft comments: pt.1 3.3.6 pair canonical form undefined?

Regarding the draft at
http://www.w3.org/TR/2004/PER-xmlschema-1-20040318/:

Section 3.3.6 says:

   PSVI Contributions for element information items

   [schema default]
     The canonical lexical representation of the
     declaration's {value constraint} value.

Is the canonical lexical representation of {value constraint}
values actually defined somehow?

Canonical lexical representations seem to be defined only for
datatypes:

   [Definition:]  A canonical lexical representation is a set of
   literals from among the valid set of literals for a datatype
   ...

However, the {value constraint} property is not defined to be
of any datatype.  It is only defined to be a pair [single quotes
represent italics]:

   {value constraint}
     Optional.  A pair consisting of a value and one of
     'default', 'fixed'.

Is does not appear that:
- "pair" is defined as some XML Schema list type (e.g., what is
   the atomic item type?), or
- the canonical representation of "a pair" is defined.



Daniel