XInclude question: parse attribute type

Section 5 of the XInclude Note declares the include element type's parse
attribute as being of type CDATA. Why isn't it an enumerated attribute
defined as (xml|text|cdata)?

Bob DuCharme          www.snee.com/bob           <bob@  
snee.com>  "The elements be kind to thee, and make thy
spirits all of comfort!" Anthony and Cleopatra, III ii