Practical, Retargetable, and Reusable real-world knowledge.
Cyc’s Knowledge Base (KB) is broadest and deepest repository of common sense knowledge, orders of magnitude more complete than anything else ever developed. The KB is not a database – it consists of real world axioms that Cyc uses to reason about the world and understand your data. Cyc’s KB includes more than 10,000 predicates, millions of collections and concepts, and more than 25 million assertions. When coupled with the inference engines, Cyc can quickly prove trillions of bits of usable, real world knowledge.
Reusable Knowledge. While the size of the KB is impressive, Cycorp’s chief goal is quality over quantity. Knowledge is represented as generally as possible so that it can be broadly reused and efficiently reasoned with. For example, rather than express that “nurses require medical training” and “doctors require medical training” and “paramedics require medical training”, Cyc only has one assertion that all medical professionals require medical training. In terms of counting, this is just one piece of knowledge, but that knowledge can be efficiently re-targeted to prove the relevant claim for any particular type of medical professional. For another example, Cyc knows that “If a conduit is pinched, then pressure builds upstream and decreases downstream.” This fact about fluid dynamics applies to blood in veins, oil in pipes, milkshakes in drinking straws, and so on.
As Expressive as the English Language. The Cyc ontology is expressed in a higher order logic. While the details of this are important and interesting to logicians, the upshot can be clearly seen in contrast with triplestores (RDF stores). Triplestores are so-called because they take three arguments: subject, object, and a relation between them. Triplestores are often represented graphically, with two nodes connected by some directed relational arrow. This is useful for saying things like the following:
Casey works as an ontologist.
The triplestore can then relate the object <Casey> to the object <ontologist> by the <works as a> relation. However, English sentences, and the propositions that they represent, are often much more complicated than these two-place relations can handle. Consider:
Casey believes that Lara performed the patient examination.
The latter part, “Lara performed the patient examination”, is amenable to a triplestore, but nesting that sentence inside a “Casey believes” component is very complicated to represent in such a framework. On the other hand, Cyc’s language, CycL, is expressive enough that you can say anything in CycL that you can say in English. This means that your valuable and naunced domain knowledge will not need to be oversimplified in order for Cyc to understand it.