Querying knowledge and data bases by a universal description logic with recursion

The main motivation of my work was to bring together three fields of Computer Science which are only apparently unrelated: Knowledge Representation, propositional logics of programs, and relational databases. Knowledge Representation as an important subfield of artificial intelligence, however, was definitely the focus of my attention: I did not consider the remaining two fields in their own right, but rather studied them from a Knowledge Representation point of view.Die vorliegende Arbeit beschäftigt sich damit, die Ausdrucksfähigkeit von Beschreibungslogiken so zu erhöhen, dass diese für praktische Zwecke einsetzbar werden. Gleichzeitig soll jedoch die Berechnungskomplexität, die selbst ausdrucksschwachen Beschreibungslogiken inhärent ist, vermieden werden