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Symbolic execution for refuting ∀∃ hyperproperties 用于驳斥∀超属性的符号执行
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-10-27 DOI: 10.1007/s00236-025-00504-z
Arthur Correnson, Tobias Nießen, Bernd Finkbeiner, Georg Weissenbacher
{"title":"Symbolic execution for refuting ∀∃ hyperproperties","authors":"Arthur Correnson,&nbsp;Tobias Nießen,&nbsp;Bernd Finkbeiner,&nbsp;Georg Weissenbacher","doi":"10.1007/s00236-025-00504-z","DOIUrl":"10.1007/s00236-025-00504-z","url":null,"abstract":"<div><p>Many important hyperliveness properties, such as refinement and generalized non-interference, fall into the class of <span>(forall exists)</span> hyperproperties, and require, for each execution trace of a system, the existence of another execution trace relating to the first one in a certain way. The alternation of quantifiers in the specification renders these hyperproperties extremely difficult to verify, or even just to test. Indeed, contrary to trace properties, where it suffices to find a single counterexample trace, refuting a <span>(forall exists)</span> hyperproperty requires not only to find a trace, but also a proof that no second trace exists that satisfies the specified relation with the first trace. As a consequence, automated testing of <span>(forall exists)</span> hyperproperties falls out of the scope of existing automated testing tools. In this paper, we present a fully automated approach to detect violations of <span>(forall exists)</span> hyperproperties in synchronous and asynchronous infinite-state systems. Our approach extends bug-finding techniques based on symbolic execution with support for trace quantification. We provide a prototype implementation of our approach, and demonstrate its effectiveness on a set of challenging examples.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 4","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00504-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145405627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Watson-Crick finite automata of small size and variants of string assembling systems 小尺寸的沃森-克里克有限自动机和串组合系统的变体
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-10-24 DOI: 10.1007/s00236-025-00510-1
András Murvai, György Vaszil
{"title":"Watson-Crick finite automata of small size and variants of string assembling systems","authors":"András Murvai,&nbsp;György Vaszil","doi":"10.1007/s00236-025-00510-1","DOIUrl":"10.1007/s00236-025-00510-1","url":null,"abstract":"<div><p>We investigate the relationship of languages characterized by variants of string assembling systems and by Watson-Crick finite automata with a small number of states. Besides the general variant, we consider so-called free, and pure string assembling systems and compare their language generating power to Watson-Crick finite automata having one state (also called stateless) and two or three states in their state sets. We also study restricted variants of models that describe unary languages.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 4","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00510-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145352587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Explainability requirements as hyperproperties 可解释性要求作为超属性
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-10-13 DOI: 10.1007/s00236-025-00507-w
Bernd Finkbeiner, Julian Siber
{"title":"Explainability requirements as hyperproperties","authors":"Bernd Finkbeiner,&nbsp;Julian Siber","doi":"10.1007/s00236-025-00507-w","DOIUrl":"10.1007/s00236-025-00507-w","url":null,"abstract":"<div><p>Explainability is emerging as a key requirement for autonomous systems. While many works have focused on what constitutes a valid explanation, few have considered formalizing explainability as a system property. In this work, we approach this problem from the perspective of hyperproperties. We start with a combination of three prominent flavors of modal logic and show how they can be used for specifying and verifying counterfactual explainability in multi-agent systems: With Lewis’ counterfactuals, linear-time temporal logic, and a knowledge modality, we can reason about whether agents know <i>why</i> a specific observation occurs, i.e., whether that observation is <i>explainable</i> to them. We use this logic to formalize multiple notions of explainability on the system level. We then show how this logic can be embedded into a hyperlogic. Notably, from this analysis we conclude that the model-checking problem of our logic is decidable, which paves the way for the automated verification of explainability requirements.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 4","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00507-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145315664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Spanning cactus and spanning cactus extension of outerplanar graphs 外平面图的生成仙人掌和生成仙人掌的扩展
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-09-24 DOI: 10.1007/s00236-025-00506-x
Chinmay Debnath, Alak Kumar Datta
{"title":"Spanning cactus and spanning cactus extension of outerplanar graphs","authors":"Chinmay Debnath,&nbsp;Alak Kumar Datta","doi":"10.1007/s00236-025-00506-x","DOIUrl":"10.1007/s00236-025-00506-x","url":null,"abstract":"<div><p>Minimum spanning cactus and minimum spanning cactus extension problems on outerplanar graphs are studied. Linear algorithms are presented for both problems on outerplanar graphs. A partitioning technique is introduced that partitions a maximal biconnected outerplanar graph into a set of maximal star-outerplanar subgraphs and some chords. Further, the minimum spanning cacti of these star-outerplanar subgraphs can be computed and suitably combined to get a minimum spanning cactus and a minimum spanning cactus extension of a given outerplanar graph.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 4","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145122436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Shortest characteristic factors of a deterministic finite automaton and computing its positive position run by pattern set matching 确定有限自动机的最短特征因子及基于模式集匹配的正位置计算
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-09-10 DOI: 10.1007/s00236-025-00484-0
Jan Janoušek, Štěpán Plachý
{"title":"Shortest characteristic factors of a deterministic finite automaton and computing its positive position run by pattern set matching","authors":"Jan Janoušek,&nbsp;Štěpán Plachý","doi":"10.1007/s00236-025-00484-0","DOIUrl":"10.1007/s00236-025-00484-0","url":null,"abstract":"<div><p>Given a deterministic finite automaton (DFA) A, we present a simple algorithm for constructing deterministic finite automata that accept the shortest forbidden factors, the shortest forbidden prefixes, the shortest forbidden suffixes, the shortest forbidden words, the shortest allowed suffixes, and the shortest allowed words of the automaton A. We refer to these sets as the shortest characteristic factors of the automaton A. If the given automaton is local, and therefore the language it accepts is strictly locally testable, the sets of its shortest characteristic factors are finite, and these automata are acyclic. Otherwise, they accept infinite languages. This approach simplifies existing methods for the extraction of forbidden factors, allows the extraction of more types of characteristic factors, and also generalizes the extraction for all classes of DFAs. Furthermore, we demonstrate that this type of extraction can be used for a sublinear run of an automaton for certain inputs. We define a positive position run of a deterministic finite automaton, representing all positions in an input string where the automaton reaches a final state. Finally, we present an algorithm for computing the positive position run of the automaton, which utilizes pattern set matching of its shortest forbidden factors and its shortest forbidden or allowed suffixes, provided that the sets are finite. We showcase the computation of the positive position run of a local automaton using backward pattern set matching, which can achieve sublinear time.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00484-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Parameterized lower bounds for the weighted vertex cover problem in trees 树中加权顶点覆盖问题的参数化下界
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-08-30 DOI: 10.1007/s00236-025-00498-8
P. Wojciechowski, K. Subramani
{"title":"Parameterized lower bounds for the weighted vertex cover problem in trees","authors":"P. Wojciechowski,&nbsp;K. Subramani","doi":"10.1007/s00236-025-00498-8","DOIUrl":"10.1007/s00236-025-00498-8","url":null,"abstract":"<div><p>In this paper, we analyze the weighted partial vertex cover problem on undirected, vertex-weighted, edge-weighted trees (WPVCT). This problem has been studied in the literature from the perspectives of exact and approximation algorithms. We investigate this problem from the perspectives of parameterization and kernelization. The WPVCT problem finds applications in a number of domains including communications, logistics and data science. This problem is defined by a number of parameters (input, output and structural). We focus on the number of vertices in the optimal cover as the parameter of interest (output parameter). One of our results is a lower bound for parameterized algorithms for the WPVCT problem. A second result is a lower bound on the number of bits in a kernel for the same problem. Both these results are based on the Exponential Time Hypothesis (ETH).</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144920536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On integer linear programs for treewidth based on perfect elimination orderings (extended version) 基于完全消去序的树宽整数线性规划（扩展版）
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-08-26 DOI: 10.1007/s00236-025-00505-y
Sven Mallach
{"title":"On integer linear programs for treewidth based on perfect elimination orderings (extended version)","authors":"Sven Mallach","doi":"10.1007/s00236-025-00505-y","DOIUrl":"10.1007/s00236-025-00505-y","url":null,"abstract":"<div><p>We analyze integer programming formulations for determining the treewidth of a graph that are based on perfect elimination orderings. For the first time, we prove structural properties that explain their limitations in providing convenient lower bounds and show how the latter are constituted. Moreover, we investigate a flow metric approach that proved promising to achieve approximation guarantees for the pathwidth of a graph, and we show why these techniques cannot be carried over to improve the addressed treewidth formulations. In addition, we present two complementary formulations for treewidth that employ positional rather than relational variables. Via computational experiments, we provide an impression on the quality and proportionality of the lower bounds on the treewidth obtained with different relaxations of perfect elimination ordering formulations.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00505-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144897056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Reasoning over n-indexed sequences in SMT 在SMT中对n索引序列进行推理
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-08-21 DOI: 10.1007/s00236-025-00496-w
Hichem Rami Ait-El-Hara, François Bobot, Guillaume Bury
{"title":"Reasoning over n-indexed sequences in SMT","authors":"Hichem Rami Ait-El-Hara,&nbsp;François Bobot,&nbsp;Guillaume Bury","doi":"10.1007/s00236-025-00496-w","DOIUrl":"10.1007/s00236-025-00496-w","url":null,"abstract":"<div><p>The SMT (Satisfiability Modulo Theories) theory of arrays is well-established and widely used, with various decision procedures and extensions developed for it. However, recent contributions suggest that developing tailored reasoning for some theories, such as sequences and strings, can be more efficient than reasoning over them through axiomatization over the theory of arrays. In this paper, we are interested in reasoning over <span>(n)</span>-indexed sequences as they are found in some programming languages, such as Ada. We propose an SMT theory of <span>(n)</span>-indexed sequences and explore different ways to represent and reason over <span>(n)</span>-indexed sequences using existing theories, as well as tailored calculi for this theory.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00496-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144880893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the 3-tree core of plane graphs 关于平面图的三树核
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-08-18 DOI: 10.1007/s00236-025-00503-0
Debajyoti Mondal, Md. Saidur Rahman
{"title":"On the 3-tree core of plane graphs","authors":"Debajyoti Mondal,&nbsp;Md. Saidur Rahman","doi":"10.1007/s00236-025-00503-0","DOIUrl":"10.1007/s00236-025-00503-0","url":null,"abstract":"<div><p>A drawing of a graph is a geometric representation of its vertices and edges. Plane 3-trees have been well studied in graph drawing literature. For many graph drawing styles, the aesthetic qualities achieved for plane 3-trees are much better than the ones known for general plane graphs. This motivates us to investigate whether one can find a large plane 3-tree type structure in a general plane graph, and if so, whether it can be leveraged to obtain a better drawing for the graph. We thus introduce the concept of a 3-tree core <i>H</i> of a 3-connected plane graph <i>G</i>. Here, <i>H</i> is an edge-labeled plane 3-tree that represents <i>G</i>, and the distance <i>d</i> between <i>H</i> and <i>G</i> is the number of vertices of <i>G</i> that are missing in <i>H</i>. As an application of this concept, we consider the planar ortho-path visibility drawing, where each vertex is drawn as an orthogonal polygonal chain on an integer grid and each edge is drawn as an orthogonal line segment between the paths corresponding to its end vertices. We show that if <i>H</i> has a flat visibility drawing (i.e., each ortho-path is a horizontal line segment) with height <i>k</i>, then <i>G</i> has an ortho-path visibility drawing with height <span>(O(k2^d))</span>. In particular, if <i>G</i> is a planar triangulation and not too distant from a 3-tree core, i.e., <span>(d=O(1))</span>, then <i>G</i> can be drawn with height <span>(4n/9+O(1))</span> by choosing an appropriate planar embedding. This bound is interesting as it is significantly smaller than the lower bound of <span>(2n/3+O(1))</span> when the ortho-path visibility drawing must respect the input embedding.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144861438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Tracy, traces, and transducers: computable counterexamples and explanations for HyperLTL model-checking Tracy，跟踪和换能器：HyperLTL模型检查的可计算反例和解释
IF 0.5 4区 计算机科学
Acta Informatica Pub Date : 2025-08-18 DOI: 10.1007/s00236-025-00499-7
Sarah Winter, Martin Zimmermann
{"title":"Tracy, traces, and transducers: computable counterexamples and explanations for HyperLTL model-checking","authors":"Sarah Winter,&nbsp;Martin Zimmermann","doi":"10.1007/s00236-025-00499-7","DOIUrl":"10.1007/s00236-025-00499-7","url":null,"abstract":"<div><p>HyperLTL model-checking enables the automated verification of information-flow properties for security-critical systems. However, it only provides a binary answer. Here, we consider the problem of computing counterexamples and explanations for HyperLTL model-checking, thereby considerably increasing its usefulness. Based on the maxim “counterexamples/explanations are Skolem functions for the existentially quantified trace variables”, we consider (Turing machine) computable Skolem functions. As not every finite transition system and formula have computable Skolem functions witnessing that the system satisfies the formula, we consider the problem of deciding whether such functions exist. Our main result shows that this problem is decidable by reducing it to solving multiplayer games with hierarchical imperfect information. Furthermore, our algorithm also computes transducers implementing such functions, if they exist.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 3","pages":""},"PeriodicalIF":0.5,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00499-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144861439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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