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A finite state Markov chain M is often viewed as a probabilistic transition system. An alternative view - which we follow here - is to regard M as a linear transform operating on the space of probability distributions over its set of nodes. The novel idea here is to discretize the probability value space [0,1] into a finite set of intervals. A concrete(More)
We propose a model of distributed timed systems where each component is a timed automaton with a set of local clocks that evolve at a rate independent of the clocks of the other components. A clock can be read by any component in the system, but it can only be reset by the automaton it belongs to. There are two natural semantics for such systems. The(More)
We consider message sequence charts enriched with timing constraints between pairs of events. As in the untimed setting, an infinite family of time-constrained message sequence charts (TC-MSCs) is generated using an HMSC—a finite-state automaton whose nodes are labelled by TC-MSCs. A timed MSC is an MSC in which each event is assigned an explicit(More)
We consider the problem of model checking message-passing systems with real-time requirements. As behavioural specifications, we use message sequence charts (MSCs) annotated with timing constraints. Our system model is a network of communicating finite state machines with local clocks, whose global behaviour can be regarded as a timed automaton. Our goal is(More)
Despite the fact that important genetic diseases are caused by mutant mitochondrial ribosomes, the molecular mechanisms by which such ribosomes result in a clinical phenotype remain largely unknown. The absence of experimental models for mitochondrial diseases has also prevented the rational search for therapeutic interventions. Here, we report on the(More)
Aminoglycoside ototoxicity has been related to a surprisingly large number of cellular structures and metabolic pathways. The finding that patients with mutations in mitochondrial rRNA are hypersusceptible to aminoglycoside-induced hearing loss has indicated a possible role for mitochondrial protein synthesis. To study the molecular interaction of(More)
Recent advances in X-ray crystallography have greatly contributed to the understanding of the structural interactions between aminoglycosides and the ribosomal decoding site. Efforts to genetically probe the functional relevance of proposed drug-nucleotide contacts have in part been hampered by the presence of multiple rRNA operons in most bacteria. A(More)
We provide a framework for distributed systems that impose timing constraints on their executions. We propose a timed model of communicating finite-state machines, which communicate by exchanging messages through channels and use event clocks to generate collections of timed message sequence charts (T-MSCs). As a specification language, we propose a monadic(More)
We consider the following decision problem: given a finite Markov chain with distinguished source and target states, and given a rational number r, does there exist an integer n such that the probability to reach the target from the source in n steps is r? This problem, which is not known to be decidable, lies at the heart of many model checking questions(More)
Timed systems, such as timed automata, are usually analyzed using their operational semantics on timed words. The classical region abstraction for timed automata reduces them to (untimed) finite state automata with the same time-abstract properties, such as state reachability. We propose a new technique to analyze such timed systems using finite tree(More)