Diagnosis
The selection rule of attribute &V1& is not the required format (forexample, average for a non-numerical attribute,AND / OR for an attribute in date ortime format, or union of sets /intersection for a single-value characteristic or afield).
This incorrect combination arises when the format of the attributechanges after the condition record has been created.

System Response
The wrong condition record results in errors in derivation.

Procedure
Delete the attribute and re-create it with a suitable selection rule.