Mathematically based techniques for the specification, development and verification of software and hardware systems. Referentially transparent languages are AMenable to symbolic manipulation allowing progrAM transformation (e.g. changing a clear inefficient specification into an obscure but efficient progrAM) and proof of correctness. {Oxford FM archive (http://www.comlab.ox.ac.uk/archive/formal-methods.html)}. (1996-05-15)