In this paper, an approach to symbolic model checking of process networks is introduced. It is based on interval decision diagrams (IDDs), a representation of multi-valued functions. Compared to other model checking strategies, IDDs show some important properties that enable the verification of process networks more adequately than with conventional approaches. Additionally, applications concerning scheduling will be shown. A new form of transition relation representation called interval mapping diagrams (IMDs)--and their less general version predicate action diagrams (PADs)--is explained together with the corresponding methods.