Interference Automata

We propose a computing model, the Two-Way Optical Interference Automata (2OIA), that makes use of the phenomenon of optical interference. We introduce this model to investigate the increase in power, in terms of language recognition, of a classical Deterministic Finite Automaton (DFA) when endowed with the facility of optical interference. The question is in the spirit of Two-Way Finite Automata With Quantum and Classical States (2QCFA) [A. Ambainis and J. Watrous, Two-way Finite Automata With Quantum and Classical States, Theoretical Computer Science, 287 (1), 299-311, (2002)] wherein the classical DFA is augmented with a quantum component of constant size. We test the power of 2OIA against the languages mentioned in the above paper. We give efficient 2OIA algorithms to recognize languages for which 2QCFA machines have been shown to exist, as well as languages whose status vis-a-vis 2QCFA has been posed as open questions. Finally we show the existence of a language that cannot be recognized by a 2OIA but can be recognized by an $O(n^3)$ space Turing machine.Comment: 19 pages. A preliminary version appears under the title "On a Model of Computation based on Optical Interference" in Proc. of the 16-th Australasian Workshop on Combinatorial Algorithms (AWOCA'05), pp. 249-26

Verifying Policy Enforcers

Policy enforcers are sophisticated runtime components that can prevent failures by enforcing the correct behavior of the software. While a single enforcer can be easily designed focusing only on the behavior of the application that must be monitored, the effect of multiple enforcers that enforce different policies might be hard to predict. So far, mechanisms to resolve interferences between enforcers have been based on priority mechanisms and heuristics. Although these methods provide a mechanism to take decisions when multiple enforcers try to affect the execution at a same time, they do not guarantee the lack of interference on the global behavior of the system. In this paper we present a verification strategy that can be exploited to discover interferences between sets of enforcers and thus safely identify a-priori the enforcers that can co-exist at run-time. In our evaluation, we experimented our verification method with several policy enforcers for Android and discovered some incompatibilities.Comment: Oliviero Riganelli, Daniela Micucci, Leonardo Mariani, and Yli\`es Falcone. Verifying Policy Enforcers. Proceedings of 17th International Conference on Runtime Verification (RV), 2017. (to appear

Contracts for Interacting Two-Party Systems

This article deals with the interrelation of deontic operators in contracts -- an aspect often neglected when considering only one of the involved parties. On top of an automata-based semantics we formalise the onuses that obligations, permissions and prohibitions on one party impose on the other. Such formalisation allows for a clean notion of contract strictness and a derived notion of contract conflict that is enriched with issues arising from party interdependence.Comment: In Proceedings FLACOS 2012, arXiv:1209.169