For an architecture to be frame-based means that it is organized around the representation of all of its knowledge in frames. This is important because it allows a uniform representation of knowledge. In a frame based system, all knowledge is represented as slots of some concept which describe properties of that concept. Frame based architectures mainatin world knowledge, redialy incorporate meta level knowledge, and are usually limited to monotonicity reasoning abilities. The prototypical frame based system is Theo by (Mitchel et. al.)