CoLAB: A hybrid knowledge representation and compilation laboratory

Knowledge bases for real-world domains such as mechanical engineering required expressive and efficient representation and processing tools. The authors pursue a declarative-compilative approach to knowledge engineering. While Horn logic (as implemented in PROLOG) is well-suited for representing relational clauses, other kinds of declarative knowledge call for hybrid extensions: functional dependencies and higher-order knowledge should be modeled directly. Forward (bottom-up) reasoning should be integrated with backward (top-down) reasoning. Constraint propagation should be used whenever possible instead of search-intensive resolution. Taxonomic knowledge should be classified into an intuitive subsumption hierarchy. The present LISP-based tools provide direct translators of these declarative representations into abstract machines such as an extended Warren abstract Machine and specialized inference engines that are interfaced to each other. More importantly, the authors provide source-to-source transformers between various knowledge types, both for user convenience and machine efficiency. These formalisms with their translators and transformers have been developed as part of CoLab, a compilation laboratory for studying what they call, respectively, ‘vertical’ and ‘horizontal’ compilation of knowledge, as well as for exploring the synergetic collaboration of the knowledge representation formalisms. A case study in the realm of mechanical engineering has been an important driving force behind the development of CoLab. It will be used as the source of examples throughout the paper when discussing the enhanced formalisms, the hybrid representation architecture, and the compilers.