  In this paper we extend PALPS, a process calculus proposed for the
spatially-explicit individual-based modeling of ecological systems, with the
notion of a policy. A policy is an entity for specifying orderings between the
different activities within a system. It is defined externally to a PALPS model
as a partial order which prescribes the precedence order between the activities
of the individu- als of which the model is comprised. The motivation for
introducing policies is twofold: one the one hand, policies can help to reduce
the state-space of a model, on the other hand, they are useful for exploring
the behavior of an ecosystem under different assumptions on the ordering of
events within the system. To take account of policies, we refine the semantics
of PALPS via a transition relation which prunes away executions that do not
respect the defined policy. Furthermore, we propose a translation of PALPS into
the probabilistic model checker PRISM . We illustrate our framework by applying
PRISM on PALPS models with policies for conducting simulation and reachability
analysis.
