HL7 v3 international datat types spec.

The datatypes spec has recursive defintions at the abstract level:
Radov, Nick wrote on the INM HL7 list:

 I've been reviewing the V3 data types and am puzzled by the definition of equality for ED http://www.hl7.org/v3ballot/html/infrastructure/datatypes/datatypes.htm#prop-ED.equal. It states that "Two values of type ED are equal if and only if their mediatype and data are equal." The mediaType property is a CS. And CS includes a code property, which is an ST. ST is a specialization of ED, and now we're back where we started. It seems like it would be impossible to implement the ED equality algorithm as specified since that would lead to infinite recursion. Is that intentional or an error in the spec?

The abstract types are included in the XSDs though and this will cause trouble. Not impossible to deal with but not so nice.