CDM: how2 create alt key using relationships

[markrem]

I know how to do this in the PDM, but not in the CDM where it also belongs. Please advise. I am using PowerDesigner 8.0.

I want to create an identifier in table X that is based on a column within table X plus the primary key from table Y. When creating an identifier in any CDM, PowerDesigner seems to limit me to including attributes of the selected table and does not appear to have a way to also select relationships.