On Generating *-Sound Nets with Substitution

We present a method for hierarchically generating sound workflow nets by substitution of nets with multiple inputs and outputs. We show that our method is correct and generalizes the class of nets generated by other hierarchical approaches. We also identify a new notion of soundness and prove that it is preserved by substitutions. We claim that this notion is better suited than *-soundness for use with hierarchical methods, while showing examples that *-soundness in the general case is not preserved by substitution.