* INTERNAL:
* Used to process primary keys and DerivedIds.
*/
protected MetadataClass getSimplePKType(){
MetadataDescriptor referenceDescriptor = getReferenceDescriptor();
ClassAccessor referenceAccessor = referenceDescriptor.getClassAccessor();
if (referenceAccessor.hasDerivedId()) {
// Referenced object has a derived ID and must be a simple pk type.
// Recurse through to get the simple type.
return ((ObjectAccessor) referenceDescriptor.getMappingAccessor(referenceDescriptor.getIdAttributeName())).getSimplePKType();
} else {
// Validate on their basic mapping.