Positive Non–Interference in Elementary and Trace Nets

Several notions of non-interference have been proposed in the literature to study the problem of confidentiality in concurrent systems. The common feature of these non-interference properties is that they are all defined as extensional properties based on some notion of behavioural equivalence on systems. Here we also address the problem of defining non-interference by looking at the structure of the net systems under investigation. We define structural non-interference properties based on the absence of particular places in the net. We characterize a structural property, called PBNI+, that is equivalent to the well-known behavioural property SBNDC. We start providing a characterization of PBNI+ on contact-free Elementary Net Systems, then we extend the definition to cope with the richer class of Trace nets.