Complexity Theoretical Results on Partitioned (Nondeterministic) Binary Decision Diagrams

Ordered binary decision diagrams (OBDDs) have found many applications in the verification of combinational and sequential circuits, protocols, and the synthesis and analysis of systems. The applications are limited, since the expressive power of polynomial-size OBDDs is too restricted. Therefore, several more general BDD models are used. Partitioned OBDDs are OBDD models allowing restricted use of nondeterminism and different variable orderings. They are restricted enough such that the essential operations can be performed efficiently and they allow polynomial-size representations for many more functions than OBDDs. Here the expressive power of polynomial-size partitioned OBDDs is investigated. A tight hierarchy with respect to the number of parts in the partition is proved and partitioned OBDDs are compared with other BDD models. Received April 1998, and in final form September 1998.