A Layer Architecture for the Integration of Rules, Inheritance, and Constraints

We informally introduce TaxLog, a close integration of logic programming and terminological reasoning. Terminological systems are handling declarative logic-based descriptions of conceptual knowledge. Most of them restrict their expressiveness and focus on (eecient) reasoning algorithms for certain services. This imposes principal restrictions on the expressivity of such a formalism. To get maximal beneet of terminological reasoning, while being able to overcome these expressiveness deeciencies, the terminological system Taxon has been integrated with logic programming by applying a CLP scheme to its assertional formalism. Because Taxon itself is an amalgamation of an abstract concept language by concrete domains (such as predicates over rational numbers) we have a three-layered system architecture: 1) rules on the basis of a tuned vocabulary which is formulated in 2) a concept language that is grounded by 3) concrete domains. We will discuss this layered architecture as a main prerequisite of several advantages in software/knowledge engineering, thus promoting a new discussion about principles of hybrid systems design (which is necessary when trying to gain practical relevance for declarative programming). 1 Motivation Newer results in knowledge representation (KR) and expert system technology suggest to turn our attention away from the idea of a uniform general-purpose language of declar-ativity towards heterogeneous hybrid systems. These ooer several distinct representation formalisms, each of them especially tailored for natural description (and eecient processing) of certain aspects of the domain knowledge.