Abstraction is an essential element in data modelling that appears mainly in one of the following forms: generalisation, classification or aggregation. In the design of complex products classification hierarchies can be found product families that are viewed as classes of product types, while product types are seen as classes of product instances. So far data models, if they support levels of classification, do not support the inheritance of product properties the way product family hierarchies are supposed to. This paper proposes an interpretation of the member of construct that enables one to define inheritance in classification hierarchies. Unified modelling language (UML) static structures are used as data modelling language. A textual notation is added that enables the introduction of data structures and corresponding data contents in the course of an analysis.