Bottom-up construction of ontologies departs from the more usual taxonomic approach to ontology development. It allows for parsimonious specification of concepts. Defined concepts are written as compact expressions that allow flexible reasoning. Obvious applications include chemistry and engineering design. For such domains, the method enables better ontologies than the taxonomic method. Taxonomic approaches remain appropriate for other applications. Bottom-up ontology construction is illustrated by presenting a drawn-out example involving an ontology of pure substances. This ontology is a simplified version of a part of the ontology developed for the Plinius project of the Knowledge-Based Systems Group, University of Twente. The viability of the approach is demonstrated by presenting a complete formalisation in pure logic programming. Chapter 1 Foreword In the Plinius project of the Knowledge-Based Systems Group at the University of Twente, ontology design is an actively pursued res...