Argument-based explanation of logic programs

The paper argues that a satisfactory explanation of a logic program must take the form of an argument, rather than a proof. This can only be done on the basis of information regarding the role of the various literals in the bodies of the clauses, which is normally not captured by such programs. A schema for arguments, derived from Toulmin, is presented, and the components of this schema are related to the roles of literals in the bodies of clauses. A metainterpreter is described that uses annotations of body literals to build up an argument structure according to this schema. This structure can then be used to present the argument in a variety of ways; this is illustrated by a discussion of how the argument structure can be used as the basis of a presentation as a paragraph of text. A simple example from a quasilegal domain is presented.