Process calculi

Null process

Process calculi generally also include a null process (variously denoted as ${\displaystyle {\mathit {nil}}}$, ${\displaystyle 0}$, ${\displaystyle {\mathit {STOP}}}$, ${\displaystyle \delta }$, or some other appropriate symbol) which has no interaction points. It is utterly inactive and its sole purpose is to act as the inductive anchor on top of which more interesting processes can be generated.