Causality in Structured Occurrence Nets

Structured occurrence nets consist of multiple occurrence nets — each recording causality and concurrency in an execution of a component of a concurrent system. These occurrence nets are linked together by means of various types of relationships, aimed at representing dependencies between communicating and evolving sub-systems. In this paper, we investigate causality in the basic class of communication structured occurrence nets (cso-nets). We start by introducing the corresponding system-level model of communication structured Place Transition Nets (cspt-nets) which extend Place Transition Nets with an explicit structuring into communicating sub-systems and process interaction based on a combination of synchronous and asynchronous communication. After that we develop a cso-net based process semantics for cspt-nets showing that causality in cso-nets is underpinned by stratified order structures extending causal partial orders with weak causality.