A collection of knowledge, usually relevant to a particular application domain, that has been formalized in an appropriate scheme to support reasoning processes. Rule-based formalisms are often used but there are other methods of knowledge representation. Knowledge bases are different from databases in that

1. (a) they not only store data but facilitate modification, revision, and other forms of internal manipulation of the knowledge,

2. (b) they are also able to handle knowledge that is incomplete (see completeness), inconsistent, and uncertain, and

3. (c) they may use imperative as well as declarative forms of knowledge.