Mary, What's Like All Cats?

ABSTRACT. In Description Logics (DL) knowledge bases (KBs) information is typically captured by crisp concepts. For many applications querying the KB by crisp query concepts is too restrictive. A controlled way of gradually relaxing a query concept can be achieved by the use of concept similarity. We formalize the task of instance query answering for crisp DL KBs using concepts relaxed by concept similarity measures (CSM). For the DL EL we investigate computation algorithms for this task, their complexity and properties for the employed CSM in case unfoldable TBoxes or general TBoxes are used.