The Produoidal Algebra of Process Decomposition

We characterize a universal normal produoidal category of monoidal contexts over an arbitrary monoidal category. In the same sense that a monoidal morphism represents a process, a monoidal context represents an incomplete process: a piece of a decomposition, possibly containing missing parts. In particular, symmetric monoidal contexts coincide with monoidal lenses and endow them with a novel universal property. We apply this algebraic structure to the analysis of multi-party protocols in arbitrary theories of processes.