ABSTRACT
Once the problem domain has been identied (see Part 1) and the necessary theoretical framework has been established (see Part 2), it is necessary to employ a suf-cient arsenal of formal tools in order to develop practical approaches to semantic integration (see Part 4). The term knowledge representation instruments is employed to collectively refer to various representation notions known as tools, technologies, mechanisms, formalisms, structures, approaches, or theories. This is the subject of the present and the subsequent chapters of Part 3. So far in this book, the issues of Knowledge (K), Representation (R), and subsequently Knowledge Representation (KR) as such have not been rigorously dened but only implicitly touched upon. This is not strange for there are at least different, not to say conicting, perspectives of K/R/KR. A thorough theoretical discussion on the matter is stimulating and interesting but of questionable practical importance and outside the scope of this book. At the practical level, however, it is important to provide a minimal framework of the most advanced, common, and interesting approaches to KR. The present chapter attempts just that.
