A graph-rewriting model of computation due to Lafont (1990). A net is built from agents (nodes) with ports; a fixed set of interaction rules rewrites pairs of connected agents. Confluent, local, and inherently parallel — the basis of optimal λ-calculus reducers (e.g. HVM).
Key facts
Each agent has one principal port and several auxiliary ports; rules fire only on principal-principal connections.
Strong confluence: any two reductions of the same redex give the same result (Church-Rosser holds trivially).
Cost model: number of interactions (β-reductions for λ encodings).