ProObj is a Prolog based system for knowledge representation which was strongly influenced by object-oriented and frame-based systems. The paper shortly describes ProObj and then presents a classification mechanism which is based on the ideas of classifiers in KL-ONE like systems.

As a new and very flexible feature we present a user-directed control of classification process. The ProObj classifier gives the user the possibility to guide the classification process by excluding attributes and facets – elements of our representation formalism – from being considered in the classification. By this mechanism we gain a substantial improvement of the efficiency of the classification process. Furthermore, it allows a more flexible and adequate modelling of a knowledge domain. It is possible to build a knowledge base under a particular view where only those attributes of concepts are considered for classification which seem to be relevant for the structure of the domain hierarchy.