Cyc contains some of the kinds of facts you’d typically find in a database, with two important differences:
All facts are tied to concepts in the knowledge base. For example, Cyc knows several hundred musicians, but it is more than a list. Since Cyc knows there are approximately 85 types things that Cyc knows every musician is. So, “Bruce Springsteen” isn’t just a string in a list of data. Cyc knows that he is a person, a professional, a social being, and many other things.
Cyc can access facts that are stored in external structured sources (such as relational databases) and treat them as if they are assertions in the knowledge base. Using Semantic Knowledge Source Integration (SKSI), Cyc automatically constructs queries to issue to these data sources, and the returned data is properly associated with concepts in the Cyc ontology.