Clarifying specialized forms of association in UML and OML

Aggregation is primarily a modelling tool. In order to assist software developersunderstand, model and represent their application, most OO methods have identi¯ed someform of aggregation (or whole-part relationship) as being useful in many situations. Oneproblem is that the various types of aggregation discussed in refs. 4{6 (Figure 1) are notsupported explicitly at the coding level. Furthermore, when discussing aggregation withany programming language expert, the concerns are not those of the con¯gurational (wherethe parts are structurally or functionally related) or the homeomerous (where the parts areof the same substance as the whole) nature of the relationship (Figure 1) but include thoseof lifetime dependency, coincident destruction and whether to use a reference, embeddedvalue or pointer.