Backward simulations are sometimes necessary, in particular, when nondeterministic choices are resolved earlier in the specification than in the implementation. Existing theory, techniques and technology are of little help as they fail to provide a global framework relating various design parameters to system dyn. Lecture Notes in Computer Science, Vol. We developed StarL as a framework for programming, simulating, and verifying distributed systems that interacts with physical processes. If R is a relation, then we denote the domain and range of R by dom R and range R , respectively.
When it was established in New York City in 1947, it stated that: The purpose of this organization would be to advance the science, development, construction, and application of the new machinery for computing, reasoning, and other handling of information. Our goal is to get a deeper insight into the state-of-the-art in this area, as well as to form a position with respect to possible needs and gaps in the current tools used by industry and academia, which need to be addressed in order to enhance the applicability of model-based testing techniques. Timed automata are state-machine-like structures used to model real-time systems. Using the fact that R is a refinement, we may infer that there is a trajectory in B from 0, true to n, true on which there are at least n + 2 states including the first and last state in which an a-action is enabled. As examples for A1 , B1 , A2 , and B2 , consider, respectively, the automata CatchUpA, CatchUpB, BoundedAlternateA, BoundedAlternateB in Figs. The above construction either ends after finitely many stages such that the last trajectory of α is admissible, or goes through infinitely many stages such that α contains infinitely many local actions.
The second reference appears in the discussion about the kinds of automata that satisfy the assumptions of Theorem 7. We demonstrate the adequacy of our framework in a representative case study where we formalize a family of well-known fault-tolerant broadcasting algorithms under a variety of failure assumptions. Reliable message delivery and conditionally-fast transactions are not possible without accurate clocks. In this section we introduce the basic notations used thought the paper and we formally define formation problems for mobile agents. Many applications involving timed systems have strong safety, reliability, and predictability requirements, which make it important to have methods for systematic design of systems and rigorous analysis of timing-dependent behavior.
Lecture Notes in Computer Science, Vol. Automated analysis of timed automata relies on the construction of a finite quotient of the infinite space of clock valuations. By definition of the edge set of G, βi , y is reachable from β1 , z. A hybrid automaton is a mathematical model for hybrid systems, which combines, in a single formalism, automaton transitions for capturing discrete change with differential equations for capturing continuous change. Let β be the trace of a closed execution fragment of A from yA with last state xA.
When any component automaton performs a discrete step involving an action a, so do all component automata that have a as an external action. In part due to these efforts, Uppaal is now routinely used for industrial case studies and has thousands of users, both in academia and industry. Since A1 and A2 are compatible, either l is not in the signature of the other automaton Aj , or l is an input action of Aj which is enabled within any state of Aj by Axiom E1. In this paper we introduce a new plugin of the toolkit, the Tempo-to-Java compiler, which automatically translates high level Tempo specification into executable Java code for various distributed platforms. Let τ1 be a trajectory of A1 with τ1. We claim that each node βi , y of G is reachable from some root β1 , z for some z.
We use σ to denote the cardinality of dom σ. Whereas automaton A has a perfect clock with rate 1, automaton B measures time with a clock that may run either too slow or too fast, in an arbitrary fashion. Roberto Segala Facebook Roberto Segala is on Facebook. Proof: The proof is straightforward except for showing that Axiom E2 is satisfied by the composition. Hybrid Systems: Computation and Control, Prague, the Czech Republic April 3—5, 2003. It includes results that capture common proof methods for showing that automata satisfy properties. The resulting model is expressive enough to describe complex timing behavior, and to express the important ideas of previous timed automata frameworks.
One of his long-term goals is to design a general mathematical model that can be used for the description and analysis of systems that exhibit stochastic hybrid behavior. On the other hand, by decomposing the proof along the lines of Corollary 8. The limit of such a chain, which contains infinitely many outputs, cannot be a trace of UseOldInputA or UseOldInputB since the number of outputs they can perform is bounded by a natural number. Software written with traditional development practices, however, likely contains bugs or unintended interactions among components, which can result in uncontrolled and possibly disastrous physical-world interactions. Computer Languages, Systems, and Structures , 28:129--154, 2002.
Potential topics include, but not are limited to: distributed algorithms and lower bounds, algorithm design methods, formal modeling and verification of distributed algorithms, and concurrent data structures. Join Facebook to connect with Roberto Segala and others you may know. Many applications involving timed systems have strong safety, reliability, and predictability requirements, which makes it important to have methods for systematic design of systems and rigorous analysis of timing-dependent behavior. All automata have the same set of actions, consisting of the external actions a and b. An important feature of this model is its support for decomposing hybrid system descriptions. Timed systems are employed in a wide range of domains including communications, embedded systems, real-time operating systems, and automated control.
When any component automaton performs a discrete step involving an action a, so do all component automata that have a as an external action. In Proceedings of Formal Methods for the Design of Real-Time Systems, volume 3185 of Lecture Notes in Computer Science, pages 237—267. Adding prophecy variables to obtain a refinement. In addition to supporting all of these features, modeling frameworks for timed systems must provide mechanisms for representing continuously evolving components such as clocks and timers. Then there exists an execution fragment α of A such that α. Then B has an execution fragment β with β. Safety is proved by inductively reasoning over the executions of the composed system automaton.