Pub Date : 2016-09-19DOI: 10.1080/00207179.2016.1216607
Ting Jiao, Y. Gan, G. Xiao, W. Wonham
We consider discrete-event systems (DES) consisting of parallel arrays of machines and buffers. The machines are divided into groups in each of which the members have identical structure, i.e. same state set and isomorphic transitions. In these systems, to avoid the underflow or overflow of the buffers, the controller only needs the information of the total numbers of components at each state and the numbers of workpieces in the buffers. By exploiting the identical structure of each group, we extract such control information from the control functions computed by the state tree structures (STS) to generate abstract control functions. Thanks to the symmetry of the system, we show that all controllable events relabeled to the same symbol share an invariant abstract control function, which is independent of the total number of machines, as long as the buffer sizes are fixed. The approach is illustrated by two examples.
{"title":"Exploiting symmetry of state tree structures for discrete-event systems with parallel components","authors":"Ting Jiao, Y. Gan, G. Xiao, W. Wonham","doi":"10.1080/00207179.2016.1216607","DOIUrl":"https://doi.org/10.1080/00207179.2016.1216607","url":null,"abstract":"We consider discrete-event systems (DES) consisting of parallel arrays of machines and buffers. The machines are divided into groups in each of which the members have identical structure, i.e. same state set and isomorphic transitions. In these systems, to avoid the underflow or overflow of the buffers, the controller only needs the information of the total numbers of components at each state and the numbers of workpieces in the buffers. By exploiting the identical structure of each group, we extract such control information from the control functions computed by the state tree structures (STS) to generate abstract control functions. Thanks to the symmetry of the system, we show that all controllable events relabeled to the same symbol share an invariant abstract control function, which is independent of the total number of machines, as long as the buffer sizes are fixed. The approach is illustrated by two examples.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134066391","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 : 2016-06-23DOI: 10.1109/WODES.2016.7497893
M. Navarro-Gutiérrez, A. Ramírez-Treviño, M. Suárez
In this work steady-state throughput changes due to firing rate variations in timed continuous Petri nets with infinite server semantics are considered. Two peculiar behaviors may appear: discontinuities and non-monotonicities. None of them are possible in Mono-T-Semiflow (MTS) nets when a certain structural condition, defined on the basis of the steady-state marking, is fulfilled. This work investigates the relation between discontinuities and non-monotonicities when the mentioned condition is not satisfied. First, using a graph-based perspective, such condition is classified using structural objects of the net. Then, the system throughput under firing rate variations is studied taking advantage of this classification. The equivalence between monotonicities and the structural condition is derived, whilst a counterexample shows that for discontinuities the implication goes in one way.
{"title":"Discontinuities and non-monotonicities in Mono-T-Semiflow timed continuous Petri nets","authors":"M. Navarro-Gutiérrez, A. Ramírez-Treviño, M. Suárez","doi":"10.1109/WODES.2016.7497893","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497893","url":null,"abstract":"In this work steady-state throughput changes due to firing rate variations in timed continuous Petri nets with infinite server semantics are considered. Two peculiar behaviors may appear: discontinuities and non-monotonicities. None of them are possible in Mono-T-Semiflow (MTS) nets when a certain structural condition, defined on the basis of the steady-state marking, is fulfilled. This work investigates the relation between discontinuities and non-monotonicities when the mentioned condition is not satisfied. First, using a graph-based perspective, such condition is classified using structural objects of the net. Then, the system throughput under firing rate variations is studied taking advantage of this classification. The equivalence between monotonicities and the structural condition is derived, whilst a counterexample shows that for discontinuities the implication goes in one way.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132190055","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 : 2016-06-23DOI: 10.1109/WODES.2016.7497850
Dipankar Maity, J. Baras
In this work, a two players nonzero-sum differential game is considered, where one player tries to minimize some predefined cost and the other tries to maximize the same. The game is described by a stochastic differential system and the actions of the players serve as the control inputs to the dynamical system. The cost being a function of the actions chosen by the players and the state of the dynamical system, the players aim to control the state in order to optimize the cost functional. However in this problem the players do not have the access to the states for every time, rather the states are available at discrete time instances after some finite costs are paid by the players. The inclusion of the information-cost makes the structure of the cost functional non-classical. The work presents the strategies for the players under no-cost information access as well as under costly information access. Explicit time instances for the information access are also derived by solving certain finite dimensional optimization problems.
{"title":"Strategies for two-player differential games with costly information","authors":"Dipankar Maity, J. Baras","doi":"10.1109/WODES.2016.7497850","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497850","url":null,"abstract":"In this work, a two players nonzero-sum differential game is considered, where one player tries to minimize some predefined cost and the other tries to maximize the same. The game is described by a stochastic differential system and the actions of the players serve as the control inputs to the dynamical system. The cost being a function of the actions chosen by the players and the state of the dynamical system, the players aim to control the state in order to optimize the cost functional. However in this problem the players do not have the access to the states for every time, rather the states are available at discrete time instances after some finite costs are paid by the players. The inclusion of the information-cost makes the structure of the cost functional non-classical. The work presents the strategies for the players under no-cost information access as well as under costly information access. Explicit time instances for the information access are also derived by solving certain finite dimensional optimization problems.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125418751","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 : 2016-06-23DOI: 10.1109/WODES.2016.7497847
S. Ebner, Sebastian Trimpe
The average communication in a typical event-based state estimation scenario is analyzed analytically and in robot experiments. A sender observes a linear Gaussian process and sporadically transmits mean and variance to a remote estimator according to an event-based protocol. By exploiting the event-based architecture, an expression for the average communication rate is obtained, which is useful for numerical computation. In addition, approximate closed-form expressions for the steady-state rate (given in terms of problem and design parameters) are derived. The analytic results for the communication rate are verified in experiments of a one-dimensional robot link.
{"title":"Communication rate analysis for event-based state estimation","authors":"S. Ebner, Sebastian Trimpe","doi":"10.1109/WODES.2016.7497847","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497847","url":null,"abstract":"The average communication in a typical event-based state estimation scenario is analyzed analytically and in robot experiments. A sender observes a linear Gaussian process and sporadically transmits mean and variance to a remote estimator according to an event-based protocol. By exploiting the event-based architecture, an expression for the average communication rate is obtained, which is useful for numerical computation. In addition, approximate closed-form expressions for the steady-state rate (given in terms of problem and design parameters) are derived. The analytic results for the communication rate are verified in experiments of a one-dimensional robot link.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125837957","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 : 2016-06-23DOI: 10.1109/WODES.2016.7497884
Dimitri Bohlender, H. Simon, Nico Friedrich, S. Kowalewski, Stefan Hauck-Stattelmann
This paper presents a technique for fully automated generation of test cases for PLC programs adhering to the IEC 61131-3 standard. While previous methods strive for completeness and therefore struggle with the state explosion we pursue a symbolic execution based approach, dropping completeness but nevertheless achieving similar or even better results in practice. The core component is a symbolic execution engine which chooses the next state to execute, handles constraints emerging during the execution and derives respective test vectors leading to a state. To make for a high coverage of the generated tests, we adopt techniques from concolic testing, allow for use of heuristics to prioritise promising states but also merge states to alleviate the path explosion. We exploit peculiarities of PLC semantics to determine reasonable merge-points and unlike similar approaches even handle unreachable code. To examine the feasibility of our technique we evaluate it on function blocks used in industry.
{"title":"Concolic test generation for PLC programs using coverage metrics","authors":"Dimitri Bohlender, H. Simon, Nico Friedrich, S. Kowalewski, Stefan Hauck-Stattelmann","doi":"10.1109/WODES.2016.7497884","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497884","url":null,"abstract":"This paper presents a technique for fully automated generation of test cases for PLC programs adhering to the IEC 61131-3 standard. While previous methods strive for completeness and therefore struggle with the state explosion we pursue a symbolic execution based approach, dropping completeness but nevertheless achieving similar or even better results in practice. The core component is a symbolic execution engine which chooses the next state to execute, handles constraints emerging during the execution and derives respective test vectors leading to a state. To make for a high coverage of the generated tests, we adopt techniques from concolic testing, allow for use of heuristics to prioritise promising states but also merge states to alleviate the path explosion. We exploit peculiarities of PLC semantics to determine reasonable merge-points and unlike similar approaches even handle unreachable code. To examine the feasibility of our technique we evaluate it on function blocks used in industry.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130226911","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 : 2016-06-22DOI: 10.1109/WODES.2016.7497820
L. Swartjes, M. Reniers, D. A. V. Beek, W. Fokkink
Although supervisory control synthesis has been around for many years, adoption is still low. A weak point of synthesis is the absence of a reporting mechanism. When an empty or unexpected supervisor is returned, it is very difficult to explain why this is the case. It is desired to return an explanation for a question, like, “Why is my supervisor empty?”. In general, the information needed to provide such an explanation is not present in the synthesized result. In this paper, causes (explanations) are generated for questions regarding the absence of behavior in the synthesized system. To this end, it is first investigated what information is needed and how it should be stored. Based on these findings, information of the influence of each requirement is encoded in the supervisor. This is done by annotating colors. The resulting so-called colored predicates can be used after synthesis to derive a cause for a given question.
{"title":"Why is my supervisor empty? Finding causes for the unreachability of states in synthesized supervisors","authors":"L. Swartjes, M. Reniers, D. A. V. Beek, W. Fokkink","doi":"10.1109/WODES.2016.7497820","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497820","url":null,"abstract":"Although supervisory control synthesis has been around for many years, adoption is still low. A weak point of synthesis is the absence of a reporting mechanism. When an empty or unexpected supervisor is returned, it is very difficult to explain why this is the case. It is desired to return an explanation for a question, like, “Why is my supervisor empty?”. In general, the information needed to provide such an explanation is not present in the synthesized result. In this paper, causes (explanations) are generated for questions regarding the absence of behavior in the synthesized system. To this end, it is first investigated what information is needed and how it should be stored. Based on these findings, information of the influence of each requirement is encoded in the supervisor. This is done by annotating colors. The resulting so-called colored predicates can be used after synthesis to derive a cause for a given question.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114713038","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 : 2016-05-30DOI: 10.1109/WODES.2016.7497866
B. Bérard, O. Kouchnarenko, J. Mullins, Mathieu Sassolas
Given a probabilistic transition system (PTS) A partially observed by an attacker, and an ω-regular predicate φ over the traces of A, measuring the disclosure of the secret φ in A means computing the probability that an attacker who observes a run of A can ascertain that its trace belongs to φ. We consider specifications given as Interval Markov Chains (IMCs), which are underspecified Markov chains where probabilities on edges are only required to belong to intervals. Scheduling an IMC S produces a concrete implementation as a PTS and we define the worst case disclosure of secret φ in S as the maximal disclosure of φ over all PTSs thus produced. We compute this value for a subclass of IMCs and we prove that simulation between specifications can only improve the opacity of implementations.
{"title":"Preserving opacity on Interval Markov Chains under simulation","authors":"B. Bérard, O. Kouchnarenko, J. Mullins, Mathieu Sassolas","doi":"10.1109/WODES.2016.7497866","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497866","url":null,"abstract":"Given a probabilistic transition system (PTS) A partially observed by an attacker, and an ω-regular predicate φ over the traces of A, measuring the disclosure of the secret φ in A means computing the probability that an attacker who observes a run of A can ascertain that its trace belongs to φ. We consider specifications given as Interval Markov Chains (IMCs), which are underspecified Markov chains where probabilities on edges are only required to belong to intervals. Scheduling an IMC S produces a concrete implementation as a PTS and we define the worst case disclosure of secret φ in S as the maximal disclosure of φ over all PTSs thus produced. We compute this value for a subclass of IMCs and we prove that simulation between specifications can only improve the opacity of implementations.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125594823","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 : 2016-05-30DOI: 10.1109/WODES.2016.7497854
Abderraouf Boussif, Baisi Liu, M. Ghazel
In this paper, an approach to analyze diagnosability of intermittent failures in discrete-event systems (DESs) is developed. The analysis is performed based on the twin-plant structure generated from the input model, which is a finite state automaton (FSA), where states are partitioned according to the predefined failure conditions of the system. Two definitions of diagnosability, regarding the occurrence of failures and their normalization (i.e., the disappearance of failures) are discussed. Necessary and sufficient conditions for diagnosability are developed and proved. Then, an incremental algorithm to actually check such conditions is elaborated. Finally, a benchmark is given to both illustrate the various concepts discussed and assess the efficiency of the proposed approach.
{"title":"A twin-plant based approach for diagnosability analysis of intermittent failures","authors":"Abderraouf Boussif, Baisi Liu, M. Ghazel","doi":"10.1109/WODES.2016.7497854","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497854","url":null,"abstract":"In this paper, an approach to analyze diagnosability of intermittent failures in discrete-event systems (DESs) is developed. The analysis is performed based on the twin-plant structure generated from the input model, which is a finite state automaton (FSA), where states are partitioned according to the predefined failure conditions of the system. Two definitions of diagnosability, regarding the occurrence of failures and their normalization (i.e., the disappearance of failures) are discussed. Necessary and sufficient conditions for diagnosability are developed and proved. Then, an incremental algorithm to actually check such conditions is elaborated. Finally, a benchmark is given to both illustrate the various concepts discussed and assess the efficiency of the proposed approach.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127730602","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497855
Mona Noori Hosseini, B. Lennartson
This paper presents an efficient diagnosability verification technique, based on a general abstraction approach. More specifically, branching bisimulation including state labels with explicit divergence (BBSD) is defined. This bisimulation preserves the temporal logic property that verifies diagnosability. Based on a proposed BBSD algorithm, compositional abstraction for modular diagnosability verification is shown to offer a significant state space reduction in comparison to state-of-the-art techniques. This is illustrated by verifying non-diagnosability analytically for a set of synchronized components, where the abstracted solution is independent of the number of components and the number of observable events.
{"title":"Diagnosability verification using compositional branching bisimulation","authors":"Mona Noori Hosseini, B. Lennartson","doi":"10.1109/WODES.2016.7497855","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497855","url":null,"abstract":"This paper presents an efficient diagnosability verification technique, based on a general abstraction approach. More specifically, branching bisimulation including state labels with explicit divergence (BBSD) is defined. This bisimulation preserves the temporal logic property that verifies diagnosability. Based on a proposed BBSD algorithm, compositional abstraction for modular diagnosability verification is shown to offer a significant state space reduction in comparison to state-of-the-art techniques. This is illustrated by verifying non-diagnosability analytically for a set of synchronized components, where the abstracted solution is independent of the number of components and the number of observable events.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114988930","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 : 2016-05-01DOI: 10.1109/WODES.2016.7497819
Kai Cai, W. Wonham
Recently we proposed relative observability for supervisory control of discrete-event systems under partial observation. Relative observability is closed under set unions and hence there exists the supremal relatively observable sublanguage of a given language. In this paper we present a new characterization of relative observability, based on which we design an algorithm that computes the supremal sublanguage. This algorithm is formulated in terms of languages, thereby separating out the linguistic essence of the problem from the implementational aspects of state computation using automaton models. Exploiting the linguistic concept of support based on Nerode equivalence, we prove that for regular languages the algorithm is finitely convergent to the supremal sublanguage.
{"title":"A new algorithm for computing the supremal relatively observable sublanguage","authors":"Kai Cai, W. Wonham","doi":"10.1109/WODES.2016.7497819","DOIUrl":"https://doi.org/10.1109/WODES.2016.7497819","url":null,"abstract":"Recently we proposed relative observability for supervisory control of discrete-event systems under partial observation. Relative observability is closed under set unions and hence there exists the supremal relatively observable sublanguage of a given language. In this paper we present a new characterization of relative observability, based on which we design an algorithm that computes the supremal sublanguage. This algorithm is formulated in terms of languages, thereby separating out the linguistic essence of the problem from the implementational aspects of state computation using automaton models. Exploiting the linguistic concept of support based on Nerode equivalence, we prove that for regular languages the algorithm is finitely convergent to the supremal sublanguage.","PeriodicalId":268613,"journal":{"name":"2016 13th International Workshop on Discrete Event Systems (WODES)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127256151","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}
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