With the persistent deployment of ontological specifications in practice and the increasing size of the deployed ontologies, methodologies for ontology engineering are becoming more and more important. In particular, the specification of negative constraints is often neglected by the human expert, whereas they are crucial for increasing an ontology's deductive potential.
We propose a novel, arguably cognitively advantageous methodology for identifying and adding missing negative constraints to an existing ontology. To this end, a domain expert navigates through the space of satisfiable class expressions with the aim of finding absurd ones, which then can be forbidden by adding a respective constraint to the ontology.
We give the formal foundations of our approach, provide an implementation, called Possible World Explorer (PEW) and illustrate its usability by describing prototypical navigation paths using the example of the well-known pizza ontology.