Name Collision in Multiple Classification Hierarchies

Resumé

Supporting multiple classification in object-oriented programming languages is the topic of discussion in this paper. Supporting multiple classification gives rise to one important question --- namely the question of inheritance of attributes with identical names from multiple paths in the classification hierarchy. The problem is to decide how these multiple classification paths are reflected in the class being defined. One of the conclusions in this paper is, that by choosing strict and simple inheritance rules, one is excluding some particular usages of multiple classification. This leads to the notion of attribute-resolution at class definition, which means that the programmer in some cases is forced or allowed to resolve the potential ambiguity of the inherited names. The concept of attribute-resolution is managed through the identification of two conceptually different utilizations of specialization (unification and intersection), and two different attribute properties (plural and singleton) to guide the attribute-resolution.