  Zero-suppressed binary decision diagrams (ZDDs) are a data structure
representing Boolean functions, and one of the most successful variants of
binary decision diagrams (BDDs). On the other hand, BDDs are also called
branching programs in computational complexity theory, and have been studied as
a computation model. In this paper, we consider ZDDs from the viewpoint of
computational complexity theory. Our main proposal of this paper is that we
regard the basic idea of ZDDs as a new computation, which we call
zero-suppressed computation. We consider the zero-suppressed version of two
classical computation models, decision trees and branching programs, and show
some results. Although this paper is mainly written from the viewpoint of
computational complexity theory, the concept of zero-suppressed computation can
be widely applied to various areas.
