Knowledge bases, data bases and object-oriented systems (referred to in the paper as Object-Centered systems) all rely on attributes as the main construct used to associate properties to objects; among these, a fundamental role is played by the so-called part-whole relation. The representation of such a structural information usually requires a particular semantics together with specialized inference and update mechanisms, but rarely do current modeling formalisms and methodologies give it a specific "first-class" dignity. The main thesis of this paper is that the part-whole relation cannot simply be considered as an ordinary attribute, its specific ontological nature requires to be understood and integrated within data modeling formalisms and methodologies. On the basis of such an ontological perspective, we survey the conceptual modeling issues involving part-whole relations, and the various modeling frameworks provided by knowledge representation and object-oriented formalisms.

. Motivated by applications that demand for the adequate representation of part-whole relations, different possibilities of representing transitive relations in terminological knowledge representation systems are investigated. A well-known concept language, ALC, is extended by three different kinds of transitive roles. It turns out that these extensions differ largely in expressiveness and computational complexity, hence this investigation gives insight into the diverse alternatives for the representation of transitive relations such as part-whole relations, family relations or partial orders in general. 1 Introduction Terminological knowledge representation systems (TKR-systems) are powerful means to represent the unambiguous, well-defined terminological knowledge in technical and other domains. Mainly, TKR-systems consist of two parts: A knowledge base, which contains the explicit concept definitions given in a so-called concept language, and an inference engine which is able to inf...

The aim of this project is to investigate what kind of terminological knowledge representation system (TKR-system) is able to support the modeling of huge chemical plants. In this highly complex modeling application, a TKR-system is the appropriate tool to serve as a user--database interface. What distinguishes TKR-systems from database systems is their ability to infer implicit knowledge from the knowledge explicitly stored in a knowledge base. TKR-systems differ among other aspects in the concept language that can be used for the representation of the application relevant knowledge. On the other hand, different kinds of knowledge from different applications ask for different concept languages. This process modeling application asks for the consideration of new concept languages and even for new constructors of these languages. To aggravate the situation, the amount of time and space needed by the reasoning services of a TKR-system increases with its expressive power. Hence the choi...

this paper, results of an investigation of part--whole relations and their relevance for a process--modeling application are given and a concept--language P with appropriate expressive power is defined. Satisfiability of concept terms in P is undecidable, hence it is necessary to drop some (but not many) of the demands made for the benefit of decidability. Several ways to handle the high complexity of inference algorithms of P are discussed.

In process engineering, as in many other application domains, the domain specific knowledge is far too complex to be described entirely using description logics. Hence this knowledge is often stored using an object-oriented system, which, because of its high expressiveness, provides only weak inference services. In particular, the process engineers at RWTH Aachen have developed a frame-like language for describing process models. In this paper, we investigate how the powerful inference services provided by a DL system can support the users of this frame-based system. In addition, we consider extensions of description languages that are necessary to represent the relevant process engineering knowledge. The application domain Process engineering is concerned with the design and operation of chemical processes that take place in large chemical plants. This engineering task includes activities like deciding on an appropriate flowsheet structure (e.g. configuration of reaction and separat...

Number restrictions are concept constructors that are available in almost all implemented description logic systems. However, even though there has lately been considerable effort on integrating expressive role constructors into description logics, the roles that may occur in number restrictions are usually of a very restricted type. Until now, only languages with number restrictions on atomic roles and inversion of atomic roles, or with number restrictions on intersection of atomic roles have been investigated in detail. In the present paper, we increase the expressive power of description languages by allowing for more complex roles in number restrictions. As role constructors, we consider composition of roles (which will be present in all our languages), and intersection, union and inversion of roles in different combinations. We will present one decidability result (for the basic language that extends ALC by number restrictions on roles with composition), and three undecidability r...