  Psi-calculi is a parametric framework for process calculi similar to popular
pi-calculus extensions such as the explicit fusion calculus, the applied
pi-calculus and the spi calculus. Mechanised proofs of standard algebraic and
congruence properties of bisimilarity apply to all calculi within the
framework. A limitation of psi-calculi is that communication channels must be
symmetric and transitive. In this paper, we give a new operational semantics to
psi-calculi that allows us to lift these restrictions and simplify some of the
proofs. The key technical innovation is to annotate transitions with a
provenance -- a description of the scope and channel they originate from. We
give mechanised proofs that our extension is conservative, and that the
standard algebraic and congruence properties of strong and weak bisimilarity
are maintained. We show correspondence with a reduction semantics and barbed
bisimulation. We show how a pi-calculus with preorders that was previously
beyond the scope of psi-calculi can be captured, and how to encode mixed choice
under very strong quality criteria.

Logic in Computer Science