Knowledge representation, which is today used in database applications, artificial intelligence (AI), software engineering, and many other disciplines of computer science has deep roots in logic and philosophy (Mainzer, 2003a, 2003b). In the beginning, there was Aristotle (384–322 B.C.) who developed logic as a precise method for reasoning about knowledge. Syllogisms were introduced as formal patterns for representing special figures of logical deductions. According to Aristotle, the subject of ontology is the study of categories of things that exist or may exist in some domain.