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We introduce Genetic Systems, a formalism inspired by genetic regulatory networks and suitable for modeling the interactions between the genes and the proteins, acting as regulatory products. The generation of new objects, representing proteins, is driven by genetic gates: a new object is produced when all the activator objects are available in the system, and no inhibitor object is available. Activators are not consumed by the application of such an evolution rule. Objects disappear because of degradation: each object is equipped with a lifetime, and the object decays when such a lifetime expires. We investigate the computational expressiveness of Genetic Systems: we show that they are Turing equivalent by providing encodings of Random Access Machines in Genetic Systems. © 2008 Elsevier B.V. All rights reserved.

We introduce Genetic P systems, a class of P systems with evolution rules inspired by the functioning of the genes. The creation of new objects - representing proteins - is driven by genetic gates: a new object is produced when all the activator objects are present, and no inhibitor object is available. Activator objects are not consumed by the application of such an evolution rule. Objects disappear because of degradation: each object is equipped with a lifetime; when such a lifetime expires, the object decays. Then, we extend the basic model with bind and release rules and repressor rules, that simulate the action of protein channels and the action of substances which connect to other objects to block their use. We provide a universality result for such a class of systems. © Springer-Verlag Berlin Heidelberg 2006

Mobile Ambients has been proposed by Cardelli and Gordon as a foundational calculus for mobile computing. Since its introduction, the computational strength as well as the decidability of properties have been investigated for several fragments and variants of the standard calculus. We tackle the problem of reachability and we characterize a public (i.e., restriction free) fragment for which it is decidable. This fragment is obtained by removing the open capability and restricting the use of replication to guarded processes. Quite surprisingly, this fragment has been shown to be Turing complete by Maffeis and Phillips.

Several notions of non-interference have been proposed in the literature to study the problem of confidentiality in nondeterministic and concurrent systems. Here we rephrase some of them – notably SNNI and BNDC – over the model of safe Place/Transition Petri Nets. 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 structural properties that are slight refinement of well-known properties such as SNNI and SBNDC. We then argue that, in order to capture all the intuitive interferences at the structural level, it is necessary to consider the net originated by the region construction, yielding the property RBNI we advocate.

We propose a functorial concurrent semantics for Petri nets extended with read and inhibitor arcs, that we call inhibitor nets. Along the lines of the seminal work by Winskel on safe (ordinary) nets, the truly concurrent semantics is given at a categorical level via a chain of coreflections leading from the category SW-IN of semi-weighted inhibitor nets to the category Dom of finitary prime algebraic domains (equivalent to the category PES of prime event structures). As an intermediate semantic model, we introduce inhibitor event structures, an event-based model able to faithfully capture the dependencies among events which arise in the presence of read and inhibitor arcs. Inhibitor event structures generalise several event structure models in the literature, like prime, asymmetric and bundle event structures.

Peer-to-peer (P2P) has recently emerged as a promising model for supporting scalable networks composed of autonomous and spontaneously cooperating entities. The key concept in P2P is decentralization: the resources, the services, as well as the control are not in charge of specialized nodes in the network, but each node (called peer in this context) is directly involved in the management of all these aspects. Besides the advantages of decentralization (autonomy, adaptability, collaboration, and dinamicity just to mention few of them) one of the main drawbacks is the impossibility to predict the topology of the network, thus leaving at run-time any decision about the management of the interaction among the peers. For this reason, we consider useful to provide the developers of P2P applications with a high-level coordination language to be exploited to program the coordination among the peers. In this paper, we present [Formula: see text], a new data-driven coordination model suitable for P2P networks, and we describe [Formula: see text], an implementation of the [Formula: see text] coordination model based on the JXTA peer-to-peer technology.

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.