Recursive nets in the box algebra

This paper presents an approach to giving a formal meaning to Petri nets defined using recursive equations. It specifically addresses this problem for the box algebra, a model of concurrent computation which combines Petri nets and standard process algebras. The paper presents a detailed investigation of the solvability of recursive equations on nets in a setting which allows an infinite number of possibly unguarded equations, each equation possibly involving infinitely many recursion variables. The main result is that by using a suitable partially ordered domain of nets, it is always possible to solve a system of equations by constructing the limit of a chain of successive approximations starting from a suitable, very simple net.