Pub Date : 2016-06-01DOI: 10.14232/actacyb.22.3.2016.2
D. Darvas, András Vörös, T. Bartha
Formal verification is becoming a fundamental step in assuring thecorrectness of safety-critical systems. Since these systems are oftenasynchronous and even distributed, their verification requires methodsthat can deal with huge or even infinite state spaces. Model checkingis one of the current techniques to analyse the behaviour of systems,as part of the verification process. In this paper a symbolic boundedmodel checking algorithm is presented that relies on efficient saturation-basedmethods. The previous approaches are extended with new bounded statespace exploration strategies. In addition, constrained saturationis also introduced to improve the efficiency of bounded model checking.Our measurements confirm that these approaches do not only offera solution to deal with infinite state spaces, but in many casesthey even outperform the original methods.
{"title":"Improving Saturation-based Bounded Model Checking","authors":"D. Darvas, András Vörös, T. Bartha","doi":"10.14232/actacyb.22.3.2016.2","DOIUrl":"https://doi.org/10.14232/actacyb.22.3.2016.2","url":null,"abstract":"Formal verification is becoming a fundamental step in assuring thecorrectness of safety-critical systems. Since these systems are oftenasynchronous and even distributed, their verification requires methodsthat can deal with huge or even infinite state spaces. Model checkingis one of the current techniques to analyse the behaviour of systems,as part of the verification process. In this paper a symbolic boundedmodel checking algorithm is presented that relies on efficient saturation-basedmethods. The previous approaches are extended with new bounded statespace exploration strategies. In addition, constrained saturationis also introduced to improve the efficiency of bounded model checking.Our measurements confirm that these approaches do not only offera solution to deal with infinite state spaces, but in many casesthey even outperform the original methods.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122303481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.14232/actacyb.22.3.2016.3
G. Agnarsson, R. Greenlaw, Sanpawat Kantabutra
This paper makes three contributions to cyber-security research. First,we define a model for cyber-security systems and the concept of acyber-security attack within the model's framework. The modelhighlights the importance of game-over components - criticalsystem components which if acquired will give an adversary the abilityto defeat a system completely. The model is based on systems thatuse defense-in-depth/layered-security approaches, as many systemsdo. In the model we define the concept of penetration cost,which is the cost that must be paid in order to break into the nextlayer of security. Second, we define natural decision and optimizationproblems based on cyber-security attacks in terms of doubly weightedtrees, and analyze their complexity. More precisely, given a treeT rooted at a vertex r, a penetrating cost edge functionc on T, a target-acquisition vertex function p on T,the attacker's budget and the game-over thresholdB,G ∈ ℚ+respectively, we consider the problem of determiningthe existence of a rooted subtree T' of T within the attacker'sbudget that is, the sum of the costs of the edges in T' is lessthan or equal to B with total acquisition value more than thegame-over threshold that is, the sum of the target values of thenodes in T' is greater than or equal to G. We prove that thegeneral version of this problem is intractable, but does admit apolynomial time approximation scheme. We also analyze the complexityof three restricted versions of the problems, where the penetrationcost is the constant function, integer-valued, and rational-valuedamong a given fixed number of distinct values. Using recursion anddynamic-programming techniques, we show that for constant penetrationcosts an optimal cyber-attack strategy can be found in polynomialtime, and for integer-valued and rational-valued penetration costsoptimal cyber-attack strategies can be found in pseudo-polynomialtime. Third, we provide a list of open problems relating to the architecturaldesign of cyber-security systems and to the model.
{"title":"On Cyber Attacks and the Maximum-Weight Rooted-Subtree Problem","authors":"G. Agnarsson, R. Greenlaw, Sanpawat Kantabutra","doi":"10.14232/actacyb.22.3.2016.3","DOIUrl":"https://doi.org/10.14232/actacyb.22.3.2016.3","url":null,"abstract":"This paper makes three contributions to cyber-security research. First,we define a model for cyber-security systems and the concept of acyber-security attack within the model's framework. The modelhighlights the importance of game-over components - criticalsystem components which if acquired will give an adversary the abilityto defeat a system completely. The model is based on systems thatuse defense-in-depth/layered-security approaches, as many systemsdo. In the model we define the concept of penetration cost,which is the cost that must be paid in order to break into the nextlayer of security. Second, we define natural decision and optimizationproblems based on cyber-security attacks in terms of doubly weightedtrees, and analyze their complexity. More precisely, given a treeT rooted at a vertex r, a penetrating cost edge functionc on T, a target-acquisition vertex function p on T,the attacker's budget and the game-over thresholdB,G ∈ ℚ+respectively, we consider the problem of determiningthe existence of a rooted subtree T' of T within the attacker'sbudget that is, the sum of the costs of the edges in T' is lessthan or equal to B with total acquisition value more than thegame-over threshold that is, the sum of the target values of thenodes in T' is greater than or equal to G. We prove that thegeneral version of this problem is intractable, but does admit apolynomial time approximation scheme. We also analyze the complexityof three restricted versions of the problems, where the penetrationcost is the constant function, integer-valued, and rational-valuedamong a given fixed number of distinct values. Using recursion anddynamic-programming techniques, we show that for constant penetrationcosts an optimal cyber-attack strategy can be found in polynomialtime, and for integer-valued and rational-valued penetration costsoptimal cyber-attack strategies can be found in pseudo-polynomialtime. Third, we provide a list of open problems relating to the architecturaldesign of cyber-security systems and to the model.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133376328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.14232/actacyb.22.3.2016.6
S. Vágvölgyi
We study OI and IO one-pass reduction sequences with term rewritesystems. We present second order decidability and undecidabilityresults on recognizable tree languages and one-pass reductions. Forleft-linear TRSs, the second order OI inclusion problem and the secondorder OI reachability problem are decidable, the second order OIjoinability problem is undecidable. For right-linear TRSs, the secondorder common IO ancestor problem is undecidable.
{"title":"One-Pass Reductions","authors":"S. Vágvölgyi","doi":"10.14232/actacyb.22.3.2016.6","DOIUrl":"https://doi.org/10.14232/actacyb.22.3.2016.6","url":null,"abstract":"We study OI and IO one-pass reduction sequences with term rewritesystems. We present second order decidability and undecidabilityresults on recognizable tree languages and one-pass reductions. Forleft-linear TRSs, the second order OI inclusion problem and the secondorder OI reachability problem are decidable, the second order OIjoinability problem is undecidable. For right-linear TRSs, the secondorder common IO ancestor problem is undecidable.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116717614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-03-07DOI: 10.14232/actacyb.22.2.2015.4
J. Brzozowski, Sylvie Davies
A (left) quotient of a language $L$ by a word $w$ is the language $w^{-1}L={xmid wxin L}$. The quotient complexity of a regular language $L$ is the number of quotients of $L$; it is equal to the state complexity of $L$, which is the number of states in a minimal deterministic finite automaton accepting $L$. An atom of $L$ is an equivalence class of the relation in which two words are equivalent if for each quotient, they either are both in the quotient or both not in it; hence it is a non-empty intersection of complemented and uncomplemented quotients of $L$. A right (respectively, left and two-sided) ideal is a language $L$ over an alphabet $Sigma$ that satisfies $L=LSigma^*$ (respectively, $L=Sigma^*L$ and $L=Sigma^*LSigma^*$). We compute the maximal number of atoms and the maximal quotient complexities of atoms of right, left and two-sided regular ideals.
{"title":"Quotient Complexities of Atoms in Regular Ideal Languages","authors":"J. Brzozowski, Sylvie Davies","doi":"10.14232/actacyb.22.2.2015.4","DOIUrl":"https://doi.org/10.14232/actacyb.22.2.2015.4","url":null,"abstract":"A (left) quotient of a language $L$ by a word $w$ is the language $w^{-1}L={xmid wxin L}$. The quotient complexity of a regular language $L$ is the number of quotients of $L$; it is equal to the state complexity of $L$, which is the number of states in a minimal deterministic finite automaton accepting $L$. An atom of $L$ is an equivalence class of the relation in which two words are equivalent if for each quotient, they either are both in the quotient or both not in it; hence it is a non-empty intersection of complemented and uncomplemented quotients of $L$. A right (respectively, left and two-sided) ideal is a language $L$ over an alphabet $Sigma$ that satisfies $L=LSigma^*$ (respectively, $L=Sigma^*L$ and $L=Sigma^*LSigma^*$). We compute the maximal number of atoms and the maximal quotient complexities of atoms of right, left and two-sided regular ideals.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117244315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-01DOI: 10.14232/actacyb.21.4.2014.6
Dávid Tengeri, F. Havasi
Many software systems today use databases to permanently store their data. Testing, bug finding and migration are complex problems in the case of databases that contain many records. Here, our method can speed up these processes if we can select a smaller piece of the database (called a slice) that contains all of the records belonging to the slicing criterion. The slicing criterion might be, for example, a record which gives rise to a bug in the program. Database slicing seeks to select all the records belonging to a specific slicing criterion. Here, we introduce the concept of database slicing and describe the algorithms and data structures necessary for slicing a given database. We define the Table-based and the Record-based slicing algorithms and we empirically evaluate these methods in two scenarios by applying the slicing to the database of a real-life application and to random generated database content.
{"title":"Database Slicing on Relational Databases","authors":"Dávid Tengeri, F. Havasi","doi":"10.14232/actacyb.21.4.2014.6","DOIUrl":"https://doi.org/10.14232/actacyb.21.4.2014.6","url":null,"abstract":"Many software systems today use databases to permanently store their data. Testing, bug finding and migration are complex problems in the case of databases that contain many records. Here, our method can speed up these processes if we can select a smaller piece of the database (called a slice) that contains all of the records belonging to the slicing criterion. The slicing criterion might be, for example, a record which gives rise to a bug in the program. Database slicing seeks to select all the records belonging to a specific slicing criterion. Here, we introduce the concept of database slicing and describe the algorithms and data structures necessary for slicing a given database. We define the Table-based and the Record-based slicing algorithms and we empirically evaluate these methods in two scenarios by applying the slicing to the database of a real-life application and to random generated database content.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"280 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127476719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-30DOI: 10.1007/978-3-662-44803-8_4
G. Dósa, L. Epstein
{"title":"The Convergence Time for Selfish Bin Packing","authors":"G. Dósa, L. Epstein","doi":"10.1007/978-3-662-44803-8_4","DOIUrl":"https://doi.org/10.1007/978-3-662-44803-8_4","url":null,"abstract":"","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121835585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-02-28DOI: 10.14232/actacyb.22.3.2016.9
Szabolcs Iván, J. Nagy-György
We give an upper bound of nn-1!-n-3! for the possible largestsize of a subsemigroup of the full transformational semigroup overn elements consisting only of nonpermutational transformations.As an application we gain the same upper bound for the syntacticcomplexity of generalized definite languages as well.
{"title":"On Nonpermutational Transformation Semigroups with an Application to Syntactic Complexity","authors":"Szabolcs Iván, J. Nagy-György","doi":"10.14232/actacyb.22.3.2016.9","DOIUrl":"https://doi.org/10.14232/actacyb.22.3.2016.9","url":null,"abstract":"We give an upper bound of nn-1!-n-3! for the possible largestsize of a subsemigroup of the full transformational semigroup overn elements consisting only of nonpermutational transformations.As an application we gain the same upper bound for the syntacticcomplexity of generalized definite languages as well.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133129883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-07-26DOI: 10.14232/actacyb.21.3.2014.3
A. Valmari
Although the halting problem is undecidable, imperfect testers that fail on some instances are possible. Such instances are called hard for the tester. One variant of imperfect testers replies "I don't know" on hard instances, another variant fails to halt, and yet another replies incorrectly "yes" or "no". Also the halting problem has three variants: does a given program halt on the empty input, does a given program halt when given itself as its input, or does a given program halt on a given input. The failure rate of a tester for some size is the proportion of hard instances among all instances of that size. This publication investigates the behaviour of the failure rate as the size grows without limit. Earlier results are surveyed and new results are proven. Some of them use C++ on Linux as the computational model. It turns out that the behaviour is sensitive to the details of the programming language or computational model, but in many cases it is possible to prove that the proportion of hard instances does not vanish.
{"title":"Asymptotic Proportion of Hard Instances of the Halting Problem","authors":"A. Valmari","doi":"10.14232/actacyb.21.3.2014.3","DOIUrl":"https://doi.org/10.14232/actacyb.21.3.2014.3","url":null,"abstract":"Although the halting problem is undecidable, imperfect testers that fail on some instances are possible. Such instances are called hard for the tester. One variant of imperfect testers replies \"I don't know\" on hard instances, another variant fails to halt, and yet another replies incorrectly \"yes\" or \"no\". Also the halting problem has three variants: does a given program halt on the empty input, does a given program halt when given itself as its input, or does a given program halt on a given input. The failure rate of a tester for some size is the proportion of hard instances among all instances of that size. This publication investigates the behaviour of the failure rate as the size grows without limit. Earlier results are surveyed and new results are proven. Some of them use C++ on Linux as the computational model. It turns out that the behaviour is sensitive to the details of the programming language or computational model, but in many cases it is possible to prove that the proportion of hard instances does not vanish.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123904973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-02-15DOI: 10.14232/actacyb.23.1.2017.11
J. Karhumäki, Aleksi Saarela, L. Zamboni
In this paper we investigate local-to-global phenomena for a new family of complexity functions of infinite words indexed by k ∈ ℕ1 ∪ { + ∞ } where ℕ1 denotes the set of positive integers. Two finite words u and v in A * are said to be k-abelian equivalent if for all x ∈ A * of length less than or equal to k, the number of occurrences of x in u is equal to the number of occurrences of x in v. This defines a family of equivalence relations ~ k on A *, bridging the gap between the usual notion of abelian equivalence (when k = 1) and equality (when k = + ∞). Given an infinite word w ∈ A ω , we consider the associated complexity function (mathcal P^{(k)}_w : mathbb N_1 rightarrow mathbb N_1) which counts the number of k-abelian equivalence classes of factors of w of length n. As a whole, these complexity functions have a number of common features: Each gives a characterization of periodicity in the context of bi-infinite words, and each can be used to characterize Sturmian words in the framework of aperiodic one-sided infinite words. Nevertheless, they also exhibit a number of striking differences, the study of which is one of the main topics of our paper.
{"title":"Variations of the Morse-Hedlund Theorem for k-Abelian Equivalence","authors":"J. Karhumäki, Aleksi Saarela, L. Zamboni","doi":"10.14232/actacyb.23.1.2017.11","DOIUrl":"https://doi.org/10.14232/actacyb.23.1.2017.11","url":null,"abstract":"In this paper we investigate local-to-global phenomena for a new family of complexity functions of infinite words indexed by k ∈ ℕ1 ∪ { + ∞ } where ℕ1 denotes the set of positive integers. Two finite words u and v in A * are said to be k-abelian equivalent if for all x ∈ A * of length less than or equal to k, the number of occurrences of x in u is equal to the number of occurrences of x in v. This defines a family of equivalence relations ~ k on A *, bridging the gap between the usual notion of abelian equivalence (when k = 1) and equality (when k = + ∞). Given an infinite word w ∈ A ω , we consider the associated complexity function (mathcal P^{(k)}_w : mathbb N_1 rightarrow mathbb N_1) which counts the number of k-abelian equivalence classes of factors of w of length n. As a whole, these complexity functions have a number of common features: Each gives a characterization of periodicity in the context of bi-infinite words, and each can be used to characterize Sturmian words in the framework of aperiodic one-sided infinite words. Nevertheless, they also exhibit a number of striking differences, the study of which is one of the main topics of our paper.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114992659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-12-01DOI: 10.14232/actacyb.20.4.2012.1
Levente Erös, Tibor Csöndes
This paper proposes methods for improving the performance of a communicatingsystem that has failed its performance test. The proposed methodsextend our earlier published model-driven performance testing method,which automatically determines whether the tested system is ableto serve the specified number of requests within a second in worstcase while serving a specified number of users simultaneously. Theunderperformance diagnostic methods presented in this paper are givenas an input the formal performance model representing the systemunder test, which was built up by our performance testing methodin the performance testing phase. The presented methods aim at improvingthe performance of the system under test to the desired level atminimal cost. One of the methods presented in this paper is a binarylinear program, while the other is a heuristic method which, accordingto our simulation results, performs efficiently.
{"title":"Model-Driven Diagnostics of Underperforming Communicating Systems","authors":"Levente Erös, Tibor Csöndes","doi":"10.14232/actacyb.20.4.2012.1","DOIUrl":"https://doi.org/10.14232/actacyb.20.4.2012.1","url":null,"abstract":"This paper proposes methods for improving the performance of a communicatingsystem that has failed its performance test. The proposed methodsextend our earlier published model-driven performance testing method,which automatically determines whether the tested system is ableto serve the specified number of requests within a second in worstcase while serving a specified number of users simultaneously. Theunderperformance diagnostic methods presented in this paper are givenas an input the formal performance model representing the systemunder test, which was built up by our performance testing methodin the performance testing phase. The presented methods aim at improvingthe performance of the system under test to the desired level atminimal cost. One of the methods presented in this paper is a binarylinear program, while the other is a heuristic method which, accordingto our simulation results, performs efficiently.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114355921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：