An Introduction to Binary Decision Diagrams

1 2 Preface This note is a short introduction to Binary Decision Diagrams. It provides some background knowledge and describes the core algorithms. More details can be found in Bryant's original paper on Reduced Ordered Binary Decision Diagrams Bry866 and the survey paper Bry922. A recent extension called Boolean Expression Diagrams is described in AH977. This note is a revision of an earlier version from fall 1996 based on versions from 1995 and 1994. The major diierences are as follows: Firstly, ROBDDs are now viewed as nodes of one global graph with one xed ordering to reeect state-of-the-art of eecient BDD packages. The algorithms have been changed and simpliied to reeect this fact. Secondly, a proof of the canonicity lemma has been added. Thirdly, the sections presenting the algorithms have been completely restructured. Finally, the project proposal has been revised. for helping me debug and improve the notes. Thanks are also due to and various people on the Internet who found typos and suggested improvements.