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Flexible Correct-by-Construction Programming 灵活的按结构校正编程
4区 数学 Q3 Computer Science Pub Date : 2023-06-07 DOI: 10.46298/lmcs-19(2:16)2023
Tobias Runge, Tabea Bordis, Alex Potanin, Thomas Thüm, Ina Schaefer
Correctness-by-Construction (CbC) is an incremental program construction process to construct functionally correct programs. The programs are constructed stepwise along with a specification that is inherently guaranteed to be satisfied. CbC is complex to use without specialized tool support, since it needs a set of predefined refinement rules of fixed granularity which are additional rules on top of the programming language. Each refinement rule introduces a specific programming statement and developers cannot depart from these rules to construct programs. CbC allows to develop software in a structured and incremental way to ensure correctness, but the limited flexibility is a disadvantage of CbC. In this work, we compare classic CbC with CbC-Block and TraitCbC. Both approaches CbC-Block and TraitCbC, are related to CbC, but they have new language constructs that enable a more flexible software construction approach. We provide for both approaches a programming guideline, which similar to CbC, leads to well-structured programs. CbC-Block extends CbC by adding a refinement rule to insert any block of statements. Therefore, we introduce CbC-Block as an extension of CbC. TraitCbC implements correctness-by-construction on the basis of traits with specified methods. We formally introduce TraitCbC and prove soundness of the construction strategy. All three development approaches are qualitatively compared regarding their programming constructs, tool support, and usability to assess which is best suited for certain tasks and developers.
构造正确性(CbC)是一种渐进式的程序构造过程,目的是构造功能正确的程序。程序是逐步构建的,并遵循一个本质上保证被满足的规范。如果没有专门的工具支持,CbC使用起来很复杂,因为它需要一组预定义的固定粒度的细化规则,这些规则是编程语言之上的附加规则。每个细化规则都引入了一个特定的编程语句,开发人员在构建程序时不能脱离这些规则。CbC允许以结构化和增量的方式开发软件以确保正确性,但是有限的灵活性是CbC的缺点。在这项工作中,我们比较了经典CbC与CbC- block和TraitCbC。两种方法CbC- block和TraitCbC都与CbC相关,但是它们具有新的语言结构,可以实现更灵活的软件构建方法。我们为这两种方法提供了一个编程指南,它类似于CbC,可以生成结构良好的程序。CbC- block通过添加精化规则来插入任何语句块,从而扩展了CbC。因此,我们引入CbC- block作为CbC的扩展。TraitCbC在特征的基础上用指定的方法实现构造正确性。我们正式引入了TraitCbC,证明了建设策略的合理性。对所有三种开发方法进行定性比较,包括它们的编程结构、工具支持和可用性,以评估哪一种最适合特定的任务和开发人员。
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引用次数: 0
Lowerbounds for Bisimulation by Partition Refinement 分区细化双仿真的下限
4区 数学 Q3 Computer Science Pub Date : 2023-05-11 DOI: 10.46298/lmcs-19(2:10)2023
Jan Friso Groote, Jan Martens, Erik. P. de Vink
We provide time lower bounds for sequential and parallel algorithms deciding bisimulation on labeled transition systems that use partition refinement. For sequential algorithms this is $Omega((m mkern1mu {+} mkern1mu n ) mkern-1mu log mkern-1mu n)$ and for parallel algorithms this is $Omega(n)$, where $n$ is the number of states and $m$ is the number of transitions. The lowerbounds are obtained by analysing families of deterministic transition systems, ultimately with two actions in the sequential case, and one action for parallel algorithms. For deterministic transition systems with one action, bisimilarity can be decided sequentially with fundamentally different techniques than partition refinement. In particular, Paige, Tarjan, and Bonic give a linear algorithm for this specific situation. We show, exploiting the concept of an oracle, that this approach is not of help to develop a faster generic algorithm for deciding bisimilarity. For parallel algorithms there is a similar situation where these techniques may be applied, too.
我们提供了时序和并行算法的时间下界,这些算法决定了使用分区细化的标记转移系统的双仿真。对于顺序算法,这是$Omega((m mkern1mu {+} mkern1mu n ) mkern-1mu log mkern-1mu n)$,对于并行算法,这是$Omega(n)$,其中$n$是状态数,$m$是转换数。通过分析确定性过渡系统族得到了下限,最终在顺序情况下具有两个动作,而在并行算法中具有一个动作。对于具有一个动作的确定性转换系统,可以使用与划分细化根本不同的技术来顺序确定双相似性。特别地,Paige, Tarjan和Bonic给出了一个针对这种特殊情况的线性算法。我们利用oracle的概念表明,这种方法无助于开发用于确定双相似性的更快的通用算法。对于并行算法,也有类似的情况可以应用这些技术。
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引用次数: 0
SAT-Inspired Higher-Order Eliminations sat启发的高阶消去
4区 数学 Q3 Computer Science Pub Date : 2023-05-08 DOI: 10.46298/lmcs-19(2:9)2023
Jasmin Blanchette, Petar Vukmirović
We generalize several propositional preprocessing techniques to higher-order logic, building on existing first-order generalizations. These techniques eliminate literals, clauses, or predicate symbols from the problem, with the aim of making it more amenable to automatic proof search. We also introduce a new technique, which we call quasipure literal elimination, that strictly subsumes pure literal elimination. The new techniques are implemented in the Zipperposition theorem prover. Our evaluation shows that they sometimes help prove problems originating from Isabelle formalizations and the TPTP library.
我们将几种命题预处理技术推广到高阶逻辑,建立在现有的一阶推广的基础上。这些技术从问题中消除了字面量、子句或谓词符号,目的是使其更适合自动证明搜索。我们还引入了一种新的技术,我们称之为准纯文字消除,它严格地包含了纯文字消除。在Zipperposition定理证明中实现了这些新技术。我们的评估表明,它们有时有助于证明源自Isabelle形式化和TPTP库的问题。
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引用次数: 1
Stateful Realizers for Nonstandard Analysis 非标准分析的有状态实现器
4区 数学 Q3 Computer Science Pub Date : 2023-04-25 DOI: 10.46298/lmcs-19(2:7)2023
Bruno Dinis, Étienne Miquey
In this paper we propose a new approach to realizability interpretations for nonstandard arithmetic. We deal with nonstandard analysis in the context of (semi)intuitionistic realizability, focusing on the Lightstone-Robinson construction of a model for nonstandard analysis through an ultrapower. In particular, we consider an extension of the $lambda$-calculus with a memory cell, that contains an integer (the state), in order to indicate in which slice of the ultrapower $cal{M}^{mathbb{N}}$ the computation is being done. We pay attention to the nonstandard principles (and their computational content) obtainable in this setting. In particular, we give non-trivial realizers to Idealization and a non-standard version of the LLPO principle. We then discuss how to quotient this product to mimic the Lightstone-Robinson construction.
本文提出了一种非标准算术可实现性解释的新方法。我们在(半)直觉可实现的背景下处理非标准分析,重点讨论了Lightstone-Robinson通过超幂的非标准分析模型的构造。特别地,我们考虑将$lambda$-演算扩展为包含一个整数(状态)的内存单元,以指示在超功率$cal{M}^{mathbb{N}}$的哪个切片中进行计算。我们关注在这种情况下可获得的非标准原理(及其计算内容)。特别是,我们给出了理想化的非平凡实现器和LLPO原理的非标准版本。然后,我们讨论了如何对这个乘积进行商,以模拟Lightstone-Robinson结构。
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引用次数: 0
Smart Choices and the Selection Monad 智能选择和选择单子
4区 数学 Q3 Computer Science Pub Date : 2023-04-20 DOI: 10.46298/lmcs-19(2:3)2023
Martin Abadi, Gordon Plotkin
Describing systems in terms of choices and their resulting costs and rewards offers the promise of freeing algorithm designers and programmers from specifying how those choices should be made; in implementations, the choices can be realized by optimization techniques and, increasingly, by machine-learning methods. We study this approach from a programming-language perspective. We define two small languages that support decision-making abstractions: one with choices and rewards, and the other additionally with probabilities. We give both operational and denotational semantics. In the case of the second language we consider three denotational semantics, with varying degrees of correlation between possible program values and expected rewards. The operational semantics combine the usual semantics of standard constructs with optimization over spaces of possible execution strategies. The denotational semantics, which are compositional, rely on the selection monad, to handle choice, augmented with an auxiliary monad to handle other effects, such as rewards or probability. We establish adequacy theorems that the two semantics coincide in all cases. We also prove full abstraction at base types, with varying notions of observation in the probabilistic case corresponding to the various degrees of correlation. We present axioms for choice combined with rewards and probability, establishing completeness at base types for the case of rewards without probability.
根据选择及其产生的成本和回报来描述系统,可以让算法设计师和程序员免于指定应该如何做出这些选择;在实现中,选择可以通过优化技术来实现,并且越来越多地通过机器学习方法来实现。我们从编程语言的角度来研究这种方法。我们定义了两种支持决策抽象的小语言:一种带有选择和奖励,另一种带有概率。我们给出了操作语义和指称语义。在第二种语言的情况下,我们考虑三种指称语义,它们在可能的程序值和预期奖励之间具有不同程度的相关性。操作语义结合了标准构造的常用语义和对可能执行策略空间的优化。表意语义是组合的,它依赖于选择单子来处理选择,并增加一个辅助单子来处理其他效果,比如奖励或概率。我们建立了两个语义在所有情况下重合的充分性定理。我们还证明了基本类型的完全抽象,在概率情况下,观察的不同概念对应于不同程度的相关。我们给出了奖励与概率结合的选择公理,建立了无概率奖励情况下基本类型的完备性。
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引用次数: 0
Inferring Symbolic Automata 推理符号自动机
4区 数学 Q3 Computer Science Pub Date : 2023-04-20 DOI: 10.46298/lmcs-19(2:5)2023
Dana Fisman, Hadar Frenkel, Sandra Zilles
We study the learnability of symbolic finite state automata (SFA), a model shown useful in many applications in software verification. The state-of-the-art literature on this topic follows the query learning paradigm, and so far all obtained results are positive. We provide a necessary condition for efficient learnability of SFAs in this paradigm, from which we obtain the first negative result. The main focus of our work lies in the learnability of SFAs under the paradigm of identification in the limit using polynomial time and data, and its strengthening efficient identifiability, which are concerned with the existence of a systematic set of characteristic samples from which a learner can correctly infer the target language. We provide a necessary condition for identification of SFAs in the limit using polynomial time and data, and a sufficient condition for efficient learnability of SFAs. From these conditions we derive a positive and a negative result. The performance of a learning algorithm is typically bounded as a function of the size of the representation of the target language. Since SFAs, in general, do not have a canonical form, and there are trade-offs between the complexity of the predicates on the transitions and the number of transitions, we start by defining size measures for SFAs. We revisit the complexity of procedures on SFAs and analyze them according to these measures, paying attention to the special forms of SFAs: normalized SFAs and neat SFAs, as well as to SFAs over a monotonic effective Boolean algebra. This is an extended version of the paper with the same title published in CSL'22.
我们研究了符号有限状态自动机(SFA)的可学习性,这是一个在软件验证中得到广泛应用的模型。关于该主题的最新文献遵循查询学习范式,到目前为止所有获得的结果都是积极的。在此范例中,我们提供了sfa有效可学习性的必要条件,并由此得到了第一个否定结果。本文研究的重点是在多项式时间和数据的极限识别范式下,sfa的可学习性及其有效可识别性的增强,这涉及到学习者可以从中正确推断目标语言的一组系统特征样本的存在。我们给出了用多项式时间和数据在极限下识别sfa的必要条件,以及sfa有效可学习性的充分条件。从这些条件中我们推导出一个正结果和一个负结果。学习算法的性能通常是目标语言表示大小的函数。由于sfa通常没有规范的形式,并且在转换谓词的复杂性和转换数量之间存在权衡,因此我们首先定义sfa的大小度量。我们重新审视了sfa程序的复杂性,并根据这些措施对其进行了分析,重点讨论了sfa的特殊形式:归一化sfa和整齐sfa,以及单调有效布尔代数上的sfa。这是CSL'22上发表的同名论文的扩展版。
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引用次数: 0
Understanding the Relative Strength of QBF CDCL Solvers and QBF Resolution 了解QBF CDCL求解器的相对强度和QBF分辨率
4区 数学 Q3 Computer Science Pub Date : 2023-04-14 DOI: 10.46298/lmcs-19(2:2)2023
Olaf Beyersdorff, Benjamin Böhm
QBF solvers implementing the QCDCL paradigm are powerful algorithms that successfully tackle many computationally complex applications. However, our theoretical understanding of the strength and limitations of these QCDCL solvers is very limited. In this paper we suggest to formally model QCDCL solvers as proof systems. We define different policies that can be used for decision heuristics and unit propagation and give rise to a number of sound and complete QBF proof systems (and hence new QCDCL algorithms). With respect to the standard policies used in practical QCDCL solving, we show that the corresponding QCDCL proof system is incomparable (via exponential separations) to Q-resolution, the classical QBF resolution system used in the literature. This is in stark contrast to the propositional setting where CDCL and resolution are known to be p-equivalent. This raises the question what formulas are hard for standard QCDCL, since Q-resolution lower bounds do not necessarily apply to QCDCL as we show here. In answer to this question we prove several lower bounds for QCDCL, including exponential lower bounds for a large class of random QBFs. We also introduce a strengthening of the decision heuristic used in classical QCDCL, which does not necessarily decide variables in order of the prefix, but still allows to learn asserting clauses. We show that with this decision policy, QCDCL can be exponentially faster on some formulas. We further exhibit a QCDCL proof system that is p-equivalent to Q-resolution. In comparison to classical QCDCL, this new QCDCL version adapts both decision and unit propagation policies.
实现QCDCL范式的QBF求解器是强大的算法,可以成功地处理许多计算复杂的应用程序。然而,我们对这些QCDCL求解器的强度和局限性的理论理解非常有限。在本文中,我们建议将QCDCL解算器形式化建模为证明系统。我们定义了可用于决策启发式和单元传播的不同策略,并产生了许多健全和完整的QBF证明系统(以及新的QCDCL算法)。对于实际QCDCL求解中使用的标准策略,我们证明了相应的QCDCL证明系统与文献中使用的经典QBF解析系统Q-resolution(通过指数分离)是不可比拟的。这与已知CDCL和分辨率是p等价的命题设置形成鲜明对比。这就提出了一个问题:对于标准QCDCL,哪些公式是困难的,因为q分辨率下界并不一定适用于QCDCL,正如我们在这里展示的那样。为了回答这个问题,我们证明了QCDCL的几个下界,包括一大类随机QBFs的指数下界。我们还介绍了对经典QCDCL中使用的决策启发式的强化,它不一定按照前缀的顺序决定变量,但仍然允许学习断言子句。我们证明了使用该决策策略,QCDCL在某些公式上可以以指数速度加快。我们进一步展示了一个p等价于q分辨率的QCDCL证明系统。与经典的QCDCL相比,这个新的QCDCL版本同时适应了决策和单元传播策略。
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引用次数: 0
Good-for-games $omega$-Pushdown Automata 适合游戏$omega$-Pushdown Automata
4区 数学 Q3 Computer Science Pub Date : 2023-02-15 DOI: 10.46298/lmcs-18(1:3)2022
Karoliina Lehtinen, Martin Zimmermann
We introduce good-for-games $omega$-pushdown automata ($omega$-GFG-PDA). These are automata whose nondeterminism can be resolved based on the input processed so far. Good-for-gameness enables automata to be composed with games, trees, and other automata, applications which otherwise require deterministic automata. Our main results are that $omega$-GFG-PDA are more expressive than deterministic $omega$- pushdown automata and that solving infinite games with winning conditions specified by $omega$-GFG-PDA is EXPTIME-complete. Thus, we have identified a new class of $omega$-contextfree winning conditions for which solving games is decidable. It follows that the universality problem for $omega$-GFG-PDA is in EXPTIME as well. Moreover, we study closure properties of the class of languages recognized by $omega$-GFG- PDA and decidability of good-for-gameness of $omega$-pushdown automata and languages. Finally, we compare $omega$-GFG-PDA to $omega$-visibly PDA, study the resources necessary to resolve the nondeterminism in $omega$-GFG-PDA, and prove that the parity index hierarchy for $omega$-GFG-PDA is infinite. This is a corrected version of the paper arXiv:2001.04392v6 published originally on January 7, 2022.
我们引入了适合游戏的$omega$-下推自动机($omega$-GFG-PDA)。这些自动机的不确定性可以根据目前处理的输入来解决。好游戏性使自动机能够与游戏,树和其他自动机组成,否则需要确定性自动机的应用程序。我们的主要结果是,$omega$- gfg - pda比确定性$omega$-下推自动机更具表现力,并且求解具有$omega$- gfg - pda指定的获胜条件的无限博弈是EXPTIME-complete的。因此,我们已经确定了一类新的$omega$-上下文无关的获胜条件,其中解决游戏是可决定的。因此,$omega$-GFG-PDA的通用性问题也存在于EXPTIME中。此外,我们还研究了$omega$- gfg - PDA识别的语言类的闭包性质,以及$omega$-下推自动机和语言的游戏性的可判定性。最后,我们将$omega$-GFG-PDA与$omega$-可见PDA进行了比较,研究了$omega$-GFG-PDA中解决不确定性所需的资源,并证明了$omega$-GFG-PDA的宇称索引层次是无限的。这是对原发表于2022年1月7日的论文arXiv:2001.04392v6的更正版。
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引用次数: 4
A Spatial Logic for Simplicial Models 简单模型的空间逻辑
IF 0.6 4区 数学 Q3 Computer Science Pub Date : 2021-05-18 DOI: 10.46298/lmcs-19(3:8)2023
M. Loreti, M. Quadrini
Collective Adaptive Systems often consist of many heterogeneous componentstypically organised in groups. These entities interact with each other byadapting their behaviour to pursue individual or collective goals. In thesesystems, the distribution of these entities determines a space that can beeither physical or logical. The former is defined in terms of a physicalrelation among components. The latter depends on logical relations, such asbeing part of the same group. In this context, specification and verificationof spatial properties play a fundamental role in supporting the design ofsystems and predicting their behaviour. For this reason, different tools andtechniques have been proposed to specify and verify the properties of space,mainly described as graphs. Therefore, the approaches generally use modelspatial relations to describe a form of proximity among pairs of entities.Unfortunately, these graph-based models do not permit considering relationsamong more than two entities that may arise when one is interested indescribing aspects of space by involving interactions among groups of entities.In this work, we propose a spatial logic interpreted on simplicial complexes.These are topological objects, able to represent surfaces and volumesefficiently that generalise graphs with higher-order edges. We discuss how thesatisfaction of logical formulas can be verified by a correct and completemodel checking algorithm, which is linear to the dimension of the simplicialcomplex and logical formula. The expressiveness of the proposed logic isstudied in terms of the spatial variants of classical bisimulation andbranching bisimulation relations defined over simplicial complexes.
集体适应系统通常由许多异质组件组成,通常以组的形式组织。这些实体通过调整自己的行为来追求个人或集体目标,从而相互作用。在这些系统中,这些实体的分布决定了一个空间可以是物理的,也可以是逻辑的。前者是根据组件之间的物理关系来定义的。后者取决于逻辑关系,例如属于同一组。在这种情况下,空间属性的规范和验证在支持系统设计和预测其行为方面起着基本作用。出于这个原因,人们提出了不同的工具和技术来指定和验证空间的性质,主要描述为图。因此,这些方法通常使用模型空间关系来描述实体对之间的接近形式。不幸的是,这些基于图的模型不允许考虑两个以上实体之间的关系,当人们对通过涉及实体组之间的相互作用来描述空间方面感兴趣时,可能会出现这种关系。在这项工作中,我们提出了一个简单复合体的空间逻辑解释。这些是拓扑对象,能够有效地表示具有高阶边的图形的表面和体积。我们讨论了如何用一种与简单、复杂和逻辑公式的维数成线性关系的正确、完备的模型检验算法来验证逻辑公式的满足性。根据在简单复合体上定义的经典双模拟和分支双模拟关系的空间变异,研究了所提出逻辑的可表达性。
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引用次数: 1
The Road Ahead 前面的路
IF 0.6 4区 数学 Q3 Computer Science Pub Date : 2021-01-01 DOI: 10.1007/978-3-030-63777-4_26
R. Antonsen
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引用次数: 0
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Logical Methods in Computer Science
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