Object metamodelling of the Whole-Part relationship

The benefits of object metamodelling are the clear and precise definition of a semantics for the modelling constructs in an object modelling language. Although this work has already been done for OML and UML, some problems remain concerning the Whole-Part relationship, also called aggregation. This paper introduces a new style of object metamodelling in order to build a general yet abstract metatype called Whole-Part (Whole,Part). Subtypes are then defined according to the possibility (or not) of mixing properties generally assigned to aggregation in the literature. All the candidate properties are partitioned into three disjoint sets: the set of primary features owned by the Whole-Part (Whole,Part) metatype, the set of implied properties resulting from the adoption of the primary properties, as well as the set of secondary features. Several "flavours" of aggregation are then constructed leading to reliable and consistent subtypes of the Whole-Part relationship.