A PO Characterisation of Reconfiguration

Abstract

We consider partial order semantics of concurrent systems in which local reconfigurations may have global side effects. That is, local changes happening to an entity may block or unblock events relating to others, namely, events in which the entity does not participate. We show that partial order computations need to capture additional restrictions about event ordering, i.e., restrictions that arise from such reconfigurations. This introduces ambiguity where different partial orders represent exactly the same events with the same participants happening in different orders, thus defeating the purpose of using partial order semantics. To remove this ambiguity, we suggest an extension of partial orders called glued partial orders. We show that glued partial orders capture all possible forced reordering arising from said reconfigurations. Furthermore, we show that computations belonging to different glued partial orders are only different due to non-determinism. We consider channeled transition systems and Petri-nets with inhibiting arcs as examples.