Probabilistic omega-automata are variants of nondeterministic automata for infinite words where all choices are resolved by probabilistic distributions. Acceptance of an infinite input word can be defined in different ways: by requiring that (i) the probability for the accepting runs is positive (probable semantics), or (ii) almost all runs are accepting (almost-sure semantics), or (iii) the probability measure of the accepting runs is greater than a certain threshold (threshold semantics). The underlying notion of an accepting run can be defined as for standard omega-automata by means of a Buechi condition or other acceptance conditions, e.g., Rabin or Streett conditions. In this paper, we put the main focus on the probable semantics and provide a summary of the fundamental properties of probabilistic omega-automata concerning expressiveness, efficiency, and decision problems.
状态最小化是自动机理论中的一个基本问题。该问题在模糊自动机的研究中也具有重要意义。然而,大多数文献只考虑模糊自动机的状态约简,而模糊自动机的状态最小化问题几乎没有涉及。因此,在本文中,我们专注于后一个问题。形式上,模糊自动机极小化问题的判定形式如下:\begin{itemize} \item Given a fuzzy automaton $\mathcal{A}$ and a natural number $k$, that is, a pair $\langle \mathcal{A}, k\rangle$, is there a $k$-state fuzzy automaton equivalent to $\mathcal{A}$? \end{itemize}我们首次证明了全序格上模糊自动机的上述问题是可判定的。为此,我们首先给出了模糊多项式方程组的概念,然后提出了一个程序来解决这些系统。然后,我们将模糊多项式方程组的可解性应用于上述极小化问题,得到了可判定性。最后,我们指出,上述问题至少是PSAPCE-完全一样难。
We consider first-order logic over the subword ordering on finite words, where each word is available as a constant. Our first result is that the $Σ_1$ theory is undecidable (already over two letters). We investigate the decidability border by considering fragments where all but a certain number of variables are alternation bounded, meaning that the variable must always be quantified over languages with a bounded number of letter alternations. We prove that when at most two variables are not alternation bounded, the $Σ_1$ fragment is decidable, and that it becomes undecidable when three variab…
数据词上的数据自动机(Data Automata on Data Words)是Bojaetczyk等人在2006年提出的一种可判定模型。类自动机是最近由Bojaczyk和Lasota提出的,它是数据自动机的一种扩展,它统一了数据字上不同的自动机模型。类自动机的非空性是不可判定的,因为类自动机可以模拟两计数器机器。本文提出了一种具有优先级条件的可判定类自动机模型,它限制了类自动机,但严格扩展了数据自动机。该模型的可判定性是通过与优先级多计数器自动机建立对应关系而获得的。这种对应关系也完成了类自动机的各种类条件和计数器机器的各种模型之间的联系。此外,该模型被应用到扩展的可判定性的结果,在数组访问程序的算法分析的Alberr,Cernandal和Weinstein。
A decidability proof for bisimulation equivalence of first-order grammars is given. It is an alternative proof for a result by Sénizergues (1998, 2005) that subsumes his affirmative solution of the famous decidability question for deterministic pushdown automata. The presented proof is conceptually simpler, and a particular novelty is that it is not given as two semidecision procedures but it provides an explicit algorithm that might be amenable to a complexity analysis.
We study synthesis of reactive systems interacting with environments using an infinite data domain. A popular formalism for specifying and modelling such systems is register automata and transducers. They extend finite-state automata by adding registers to store data values and to compare the incoming data values against stored ones. Synthesis from nondeterministic or universal register automata is undecidable in general. However, its register-bounded variant, where additionally a bound on the number of registers in a sought transducer is given, is known to be decidable for universal register …
We study synthesis of reactive systems interacting with environments using an infinite data domain. A popular formalism for specifying and modelling such systems is register automata and transducers. They extend finite-state automata by adding registers to store data values and to compare the incoming data values against stored ones. Synthesis from nondeterministic or universal register automata is undecidable in general. However, its register-bounded variant, where additionally a bound on the number of registers in a sought transducer is given, is known to be decidable for universal register …
We introduce an automata model for describing interesting classes of differential privacy mechanisms/algorithms that include known mechanisms from the literature. These automata can model algorithms whose inputs can be an unbounded sequence of real-valued query answers. We consider the problem of checking whether there exists a constant $d$ such that the algorithm described by these automata are $dε$-differentially private for all positive values of the privacy budget parameter $ε$. We show that this problem can be decided in time linear in the automaton's size by identifying a necessary and s…
Parikh automata on finite words were first introduced by Klaedtke and Rueß [Automata, Languages and Programming, 2003]. In this paper, we introduce several variants of Parikh automata on infinite words and study their expressiveness. We show that one of our new models is equivalent to synchronous blind counter machines introduced by Fernau and Stiebe [Fundamenta Informaticae, 2008]. All our models admit ε-elimination, which to the best of our knowledge is an open question for blind counter automata. We then study the classical decision problems of the new automata models.
We consider linear cost-register automata (equivalent to weighted automata) over the semiring of nonnegative rationals, which generalise probabilistic automata. The two problems of boundedness and zero isolation ask whether there is a sequence of words that converge to infinity and to zero, respectively. In the general model both problems are undecidable so we focus on the copyless linear restriction. There, we show that the boundedness problem is decidable. As for the zero isolation problem we need to further restrict the class. We obtain a model, where zero isolation becomes equivalent to un…
Parikh automata extend finite automata by counters that can be tested for membership in a semilinear set, but only at the end of a run, thereby preserving many of the desirable algorithmic properties of finite automata. Here, we study the extension of the classical framework onto infinite inputs: We introduce reachability, safety, Büchi, and co-Büchi Parikh automata on infinite words and study expressiveness, closure properties, and the complexity of verification problems. We show that almost all classes of automata have pairwise incomparable expressiveness, both in the deterministic and the n…