You can derive both attributes and association ends.

When it comes to sub-classes that inherit classes that have anything derived, you may want to override the existing derivations.

You can do this in the Derivation Expressions tool:

Consider this model:

The Green-side subclasses 2,3 match the pink-side subclasses 5,6. It would be good to have a derived association that matches 1 and 4 whatever the subclass is.

1. Implement the derived link and set the OCL implementation to Class4.nullvalue - it will not be used if your Class1 is abstract.
2. On class3, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class5 (valid since Class5 is a Class4)
3. On class2, click on DerivationExpressions - find the Class4Derived expression - replace it with ocl: self.Class6 (valid since Class5 is a Class4)

You have now overridden the dummy default implementation ( Class4.nullvalue) to something valid in the context of the subclass.