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arXiv 1107.1206cs.FLcs.LO
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概率自动机之间距离的计算

Computing Distances between Probabilistic Automata

Mathieu Tracol, Josée Desharnais, Abir Zhioua

摘要:

我们提出了概率自动机(PA)上的模拟和互模拟的宽松概念,允许一些误差epsilon。当λ为零时,我们恢复PA上的互模拟和模拟的通常概念。我们给出了这些概念的逻辑特征,通过选择适当的逻辑,它不同于基本的,L与否定和L没有否定,由模态算子。使用流网络,我们展示了如何计算PTIME中的关系。这允许定义PA的状态之间的有效可计算的非折扣距离。引入了对该距离的自然修改,以获得折扣距离,从而削弱了长期转换的影响。我们比较我们的概念的距离,以前定义的其他人,并说明我们的方法上的各种例子。我们还表明,我们的距离是不膨胀的过程代数算子。虽然没有否定的L是一个合适的逻辑,以确定性PA的双(双)模拟,它不是一般的PA;有趣的是,我们证明,它确实是一个较弱的概念,称为先验双(双)模拟,我们证明是NP-难以决定。

英文摘要:

We present relaxed notions of simulation and bisimulation on Probabilistic Automata (PA), that allow some error epsilon. When epsilon is zero we retrieve the usual notions of bisimulation and simulation on PAs. We give logical characterisations of these notions by choosing suitable logics which differ from the elementary ones, L with negation and L without negation, by the modal operator. Using flow networks, we show how to compute the relations in PTIME. This allows the definition of an efficiently computable non-discounted distance between the states of a PA. A natural modification of this distance is introduced, to obtain a discounted distance, which weakens the influence of long term transitions. We compare our notions of distance to others previously defined and illustrate our approach on various examples. We also show that our distance is not expansive with respect to process algebra operators. Although L without negation is a suitable logic to characterise epsilon-(bi)simulation on deterministic PAs, it is not for general PAs; interestingly, we prove that it does characterise weaker notions, called a priori epsilon-(bi)simulation, which we prove to be NP-difficult to decide.

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