cdata attribute value normalization in schema?

How do I represent an Attribute of being type CDATA so that the further
normalization represented here 
"øåØåIf the attribute type is not CDATA, then the XML processor MUST further
process the normalized attribute value by discarding any leading and
trailing space (#x20) characters, and by replacing sequences of space (#x20)
characters by a single space (#x20) character.
" is not done? Should I use whiteSpace facet replace since that corresponds
to the rest of the algorithm?
If so, how is this okay by the xml spec as the spec says that this
normalization must be done prior to being passed to validation? 



Thanks for any help

Bryan Rasmussen