Process Ordering in a Process Calculus for Spatially-Explicit Ecological Models

TL;DR

This paper extends the PALPS process calculus for ecological modeling by introducing policies that specify activity orderings, reducing state-space and enabling exploration of different event sequences, with a translation to PRISM for analysis.

Contribution

It introduces policies into PALPS, refining its semantics and providing a translation to PRISM for simulation and reachability analysis.

Findings

Policies help reduce the state-space of models.

Policies enable exploration of different activity orderings.

The translation to PRISM facilitates analysis of ecological models.

Abstract

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.