the knowledge-based approach to the automation of program understanding presented here plays an important role in nearly all software related tasks: it is vital to the development, maintenance and re-use activities, and is indispensable in improving the quality of software development. the approach described generates rigorous program documentation mechanically by combining and building on the strengths of a practical program decomposition method, the axiomatic correctness notation, and the knowledge-based analysis approach. audience: computer science students at the advanced graduate level and researchers and practitioners interested in software development, maintenance and re-use. suitable as a secondary text for graduate level courses in software engineering and logic programming, and as a reference for researchers and practitioners in industry.