KERML — deriveFeatureType is not correct

The deriveFeatureType constraint recursively accesses the types of the subsetted Features of a Feature. However, it does not take into account that subsetting relationships may be circular.

Also, the description of the constraint states "If a Feature has chainingFeatures, then its types are the same as the last chainingFeature." However, the OCL actually unions the types of the last chainingFeature with the others.

Correct description and OCL for deriveFeatureType

The description of the constraint is revised to be consistent with the OCL, and the OCL is revised to handle circular subsetting relationships.