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.