This monograph aims to provide a powerful general-purpose proof tech-
nique for the verification of systems, whether finite or infinite. It
extends the idea of finite local model-checking, which was introduced by
Stirling and Walker: rather than traversing the entire state space of a
model, as is done for model-checking in the sense of Emerson, Clarke et
ai. (checking whether a (finite) model satisfies a formula), local
model-checking asks whether a particular state satisfies a formula, and
only explores the nearby states far enough to answer that question. The
technique used was a tableau method, constructing a tableau according to
the formula and the local structure of the model. This tableau technique
is here generalized to the infinite case by considering sets of states,
rather than single states; because the logic used, the propositional
modal mu-calculus, separates simple modal and boolean connectives from
powerful fix-point operators (which make the logic more expressive than
many other temporal logics), it is possible to give a rela- tively
straightforward set of rules for constructing a tableau. Much of the
subtlety is removed from the tableau itself, and put into a relation on
the state space defined by the tableau-the success of the tableau then
depends on the well-foundedness of this relation. The generalized
tableau technique is exhibited on Petri nets, and various standard
notions from net theory are shown to playa part in the use of the
technique on nets-in particular, the invariant calculus has a major
role.