1,519 research outputs found
VERSA: A Tool for the Specification and Analysis of Resource-Bound Real-Time Systems
VERSA is a tool that assists in the algebraic analysis of real-time systems. It is based on ACSR, a timed process algebra designed to express resource-bound real-time distributed systems. VERSA supports the analysis of real-time processes through algebraic rewriting, interactive execution, and equivalence testing. This paper begins by presenting a brief overview of the process algebra ACSR, its syntax, operational semantics, and equivalence relations. VERSA\u27S process and command syntax, its algebraic rewrite system, and its state-based analysis features are described fully. The presentation includes examples that illustrate the salient features of ACSR, and output from sample VERSA sessions that demonstrate the application of the tool to real-time systems analysis
Read Operators and their Expressiveness in Process Algebras
We study two different ways to enhance PAFAS, a process algebra for modelling
asynchronous timed concurrent systems, with non-blocking reading actions. We
first add reading in the form of a read-action prefix operator. This operator
is very flexible, but its somewhat complex semantics requires two types of
transition relations. We also present a read-set prefix operator with a simpler
semantics, but with syntactic restrictions. We discuss the expressiveness of
read prefixes; in particular, we compare them to read-arcs in Petri nets and
justify the simple semantics of the second variant by showing that its
processes can be translated into processes of the first with timed-bisimilar
behaviour. It is still an open problem whether the first algebra is more
expressive than the second; we give a number of laws that are interesting in
their own right, and can help to find a backward translation.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407
A general conservative extension theorem in process algebras with inequalities
We prove a general conservative extension theorem for transition system based process theories with easy-to-check and reasonable conditions. The core of this result is another general theorem which gives sufficient conditions for a system of operational rules and an extension of it in order to ensure conservativity, that is, provable transitions from an original term in the extension are the same as in the original system. As a simple corollary of the conservative extension theorem we prove a completeness theorem. We also prove a general theorem giving sufficient conditions to reduce the question of ground confluence modulo some equations for a large term rewriting system associated with an equational process theory to a small term rewriting system under the condition that the large system is a conservative extension of the small one. We provide many applications to show that our results are useful. The applications include (but are not limited to) various real and discrete time settings in ACP, ATP, and CCS and the notions projection, renaming, stage operator, priority, recursion, the silent step, autonomous actions, the empty process, divergence, etc
Timed Automata Semantics for Analyzing Creol
We give a real-time semantics for the concurrent, object-oriented modeling
language Creol, by mapping Creol processes to a network of timed automata. We
can use our semantics to verify real time properties of Creol objects, in
particular to see whether processes can be scheduled correctly and meet their
end-to-end deadlines. Real-time Creol can be useful for analyzing, for
instance, abstract models of multi-core embedded systems. We show how analysis
can be done in Uppaal.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499
Strategic Executions of Choreographed Timed Normative Multi-Agent Systems
This paper proposes a combined mechanism for coordinating agents in timed normative multi-agent systems. Timing constraints in a multi-agent system make it possible to force action execution to happen before certain time invariants are violated. In such multiagent systems we achieve coordination at two orthogonal levels with respect to states and actions. On the one hand, the behaviour of
individual agents is regulated by means of social and organisational inspired concepts like norms and sanctions. On the other hand, the behaviour of sets of agents is restricted according to action-based coordination mechanisms called choreographies. In both cases, the
resulting behaviour is constrained by time
Verifying P Systems with Costs by Using Priced-Timed Maude
We consider P systems that assigns storage costs per step to membranes,
and execution costs to rules. We present an abstract syntax of the new class of membrane
systems, and then deal with costs by extending the operational semantics of P systems
with promoters, inhibitors and registers.We use Priced-Timed Maude to implement the P
systems with costs. By using such a rewriting engine which corresponds to the semantics
of membrane systems with costs, we are able to prove the operational correctness of this
implementation. Based on such an operational correspondence, we can analyze properly
the evolutions of the P systems with costs, and verify several reachability properties,
including the cost of computations that reach a given membrane con guration. This
approach opens the way to various optimization problems related to membrane systems,
problems making sense in a bio-inspired model which now can be veri ed by using a
complex software platform
An executable Theory of Multi-Agent Systems Refinement
Complex applications such as incident management, social simulations, manufacturing applications, electronic auctions, e-institutions, and business to business applications are pervasive and important nowadays. Agent-oriented methodology is an advance in abstractionwhich can be used by software developers to naturally model and develop systems for suchapplications. In general, with respect to design methodologies, what it may be important tostress is that control structures should be added at later stages of design, in a natural top-downmanner going from speciļ¬cations to implementations, by reļ¬nement. Too much detail (be itfor the sake of efļ¬ciency) in speciļ¬cations often turns out to be harmful. To paraphrase D.E.Knuth, āPremature optimization is the root of all evilā (quoted in āThe Unix ProgrammingEnvironmentā by Kernighan and Pine, p. 91).The aim of this thesis is to adapt formal techniques to the agent-oriented methodologyinto an executable theory of reļ¬nement. The justiļ¬cation for doing so is to provide correctagent-based software by design. The underlying logical framework of the theory we proposeis based on rewriting logic, thus the theory is executable in the same sense as rewriting logicis. The storyline is as follows. We ļ¬rst motivate and explain constituting elements of agentlanguages chosen to represent both abstract and concrete levels of design. We then proposea deļ¬nition of reļ¬nement between agents written in such languages. This notion of reļ¬nement ensures that concrete agents are correct with respect to the abstract ones. The advantageof the deļ¬nition is that it easily leads to formulating a proof technique for reļ¬nement viathe classical notion of simulation. This makes it possible to effectively verify reļ¬nement bymodel-checking. Additionally, we propose a weakest precondition calculus as a deductivemethod based on assertions which allow to prove correctness of inļ¬nite state agents. Wegeneralise the reļ¬nement relation from single agents to multi-agent systems in order to ensure that concrete multi-agent systems reļ¬ne their abstractions. We see multi-agent systemsas collections of coordinated agents, and we consider coordination artefacts as being basedeither on actions or on normative rules. We integrate these two orthogonal coordinationmechanisms within the same reļ¬nement theory extended to a timed framework. Finally, wediscuss implementation aspects.LEI Universiteit LeidenFoundations of Software Technolog
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