Multiple key/key symbol spaces

With ID/IDREF there is only a single symbol space, ie a single ID/IDREF
table.  For example, if you are writing a technical doc you might want to
have a symbol space for the names of functions and a symbol space for the
names of terms.  <termRef> elements would have to term names and
<functionRef> elements would have to contain function names. In our ID/IDREF
replacement mechanism to we need to support multiple symbol spaces?

James