A formal model of explanation

As information systems become more complex, formal methods offer a solution to the increasing problem of ensuring correctness of design and implementation. This paper illustrates the use of mathematical specification to formalise the notion of explanation. This is relevant to any information system which engages in inference. An information system is regarded as a homogeneous function on states of information. An explanation for a conclusion is regarded as a weakening of the theory relating input to output, such that the same conclusion is reached. As an example, the specification is implemented for a simple statistical classifier to assist medical diagnosis.