Derrick Newton
CSRG seminar on 8 February 2008 at 12:00
Room 217, School of Computer Science

Applied fusion calculus - modelling communicating processes with dynamic global constraints

Workflow-based access control (WBAC) extends traditional authorisation models to represent business processes and business rules more accurately. A significant problem when modelling WBAC is to ensure that a particular business rule, namely dynamic separation of duties, is properly implemented within the model. A complete implementation of separation of duties represents a dynamic global constraint that requires some notion of history within the model. I intend to model WBAC with a process calculus. Current process calculi, particularly the applied pi-calculus, enable modelling of process and communication dynamics together with static constraints and a concept of secrecy. However, they are not well suited to the modelling of global constraints and history. I outline some properties of another family of calculi, namely concurrent constraint calculi, that are relevant to the problem of modelling dynamic global constraints. Subsequently, I introduce Bjorn Victor's fusion calculus that extends Milner's pi-calculus and provides isomorphisms with a specific family of concurrent constraint calculi. Finally, I propose an extension of the fusion calculus using applied pi-calculus constructs so as to enable the modelling of dynamic constraints and to provide a complete modelling environment for WBAC.