We develop in this paper a monitoring approach for Discrete Event Systems (DES) starting from a t... more We develop in this paper a monitoring approach for Discrete Event Systems (DES) starting from a time Petri net model representing the a priori known behavior of such a system. The originality of our approach lies in the combination made of the concept of event observability with the exploitation of the temporal constraints on these events in order to refine the result of the monitoring process.
International Journal of Soft Computing and Software Engineering, 2012
Systems' requirements are usually written in a natural language since it generally means a greate... more Systems' requirements are usually written in a natural language since it generally means a greater understanding among the various stakeholders. However, using an informal language potentially gives rise to interpretation problems, which are to be resolved prior to using (automated) verification techniques. This article tackles an important issue pertaining to requirement engineering: how to guide and help requirements' formalization? In order to support the formalization process, we propose a methodology based on a formal structure, which is the corner stone of the refinement process. The operating mode of the refinement process is highly iterative: the aforementioned structure is constructed incrementally until its validity is formally obtained. Although this process is formally backed up, it is a fundamentally subjective one, which means that interpretation errors can still occur. In case of errors, it is essential to be able to backtrack refinements until an interpretation error is found. This is why we require that each refinement be associated with a justification which may subsequently be analyzed in case an error occurred during the verification phase. This formalization process was designed to be used alongside an (unspecific) engineering process, in charge of the implementation. Once the formalization is complete, it is checked against the implementation using testing techniques, or directly against an implementation model via model-checking.
2016 13th International Workshop on Discrete Event Systems (WODES), 2016
In this paper, an approach to analyze diagnosability of intermittent failures in discrete-event s... more 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.
This paper deals with fault diagnosis of timed discrete event systems (TDESs), using a nondetermi... more This paper deals with fault diagnosis of timed discrete event systems (TDESs), using a nondeterministic model named labeled time Petri net (LTPN). Thanks to a skillful splitting of time intervals assigned to the LTPN transitions, analyzing diagnosability in such a timed context can be performed using techniques from the untimed context. Moreover, a deterministic structure called augmented state class set graph (ASG) is built on the fly, for both analyzing (∆-)diagnosability and deriving an online diagnoser.
ABSTRACT Système d'information (1) d'un usager à l'approche d'un ... more ABSTRACT Système d'information (1) d'un usager à l'approche d'un passage à niveau (3), caractérisé en ce qu'il comporte un dispositif d'information (2), monté au niveau d'un passage à niveau (3), et un équipement terminal de navigation (4) mobile, embarqué dans un véhicule (5) ou porté par un piéton, ledit dispositif d'information (2) comportant des moyens pour déterminer des données d'état dudit passage à niveau, et des moyens pour générer, à partir desdites données d'état, un message d'état du passage à niveau, ledit message d'état comportant en outre une géolocalisation dudit passage à niveau (3), ledit dispositif d'information (2) comportant des moyens de radiocommunication sans fil (10) aptes à transmettre ledit message d'état généré audit équipement terminal de navigation (4).
Dans cet article, nous présentons une approche qui permet de résoudre le problème de la Kdiagnost... more Dans cet article, nous présentons une approche qui permet de résoudre le problème de la Kdiagnosticabilité des réseaux de Petri (RdP) synchronisés et bornés. Tout d'abord, nous introduisons deux nouveaux concepts : la matrice d'incidence étendue qui intègre les informations relatives aux affectations des événements aux transitions, et le marquage étendu ainsi que l'équation d'état étendue, qui permet de transcrire le nombre d'occurrences de chaque événement depuis l'état initial, jusqu'à un certain marquage étendu cible. Sur la base de ces concepts, nous élaborons un nouvel algorithme d'analyse, à la volée, de la K-diagnosticabilité des RdP synchronisés partiellement observables. L'algorithme développé se base sur des procédures récursives et ne nécessite pas une construction a priori du graphe de marquage ni d'un diagnostiqueur.
Works in the field of verification systems have shown the critical importance of time. The nonsat... more Works in the field of verification systems have shown the critical importance of time. The nonsatisfaction of time may have important consequences for both security and performance points of view. For automated systems with level of security, the verification of time requirements is an essential part of the process validation system. In this paper, we are laying the foundations for a new and systematic approach for the verification of discrete event systems with time constraints. The contribution of this approach is threefold: first, unlike existing approaches, it allows for the verification of several requirements at once. Therefore, the approach is generic because we focus on developing mechanisms that take into account different types of requirements rather than the system to be verified. Finally, the implementation of the approach is almost as systematic because the verification tools we are developing are based on the instantiation of patterns. These patterns are designed on the basis of a classification of temporal requirements that we have established. The concepts of parallelism and hierarchy which characterize the Stocharts formalism compared to other state-transitions models help us build the foundations of our approach. An example of application to the control-command in the railway field is presented to illustrate the key concepts of our approach and its implementation.
The paper deals with monitoring experts' models in order to integrate them in a global reference ... more The paper deals with monitoring experts' models in order to integrate them in a global reference framework, which takes into account the different viewpoints relating to the design and exploitation of automated production systems. Metamodelling is used to obtain a single language of modelling and integration is used to obtain a single global model, which offers an overall coherent interpretation of the different viewpoints.
This work presents a method for verifying temporal requirements of time-constrained systems. The ... more This work presents a method for verifying temporal requirements of time-constrained systems. The method predates by establishing a new time constraints (properties) taxonomy. Then, a basis of observation patterns relative to the predefined requirements is developed. Our approach allows the automated verification of temporal requirements, initially expressed in a semi-formal formalism, through model transformation and modelchecking. The contributions of the paper are: the definition of a new time constraints (properties) typology as well as a basis of appropriate State Machines (SM) observation patterns. The second contribution consists in developing an algorithm for transforming UML SM with time annotations into Timed Automata (TA). In practice, in order to verify the temporal aspects of a given specification, the observation patterns relative to the investigated properties are instantiated to make appropriate observers. Then using our transformation algorithm, the system specification (denoted in the shape of an UML SM model) with time annotations as well as the obtained observers are translated into TA models. The TA system model is next synchronized with the TA observers. Thereby, the verification process is reduced to a reachability analysis.
This paper deals with analysis of diagnosability and K-diagnosability of dynamic systems in a mod... more This paper deals with analysis of diagnosability and K-diagnosability of dynamic systems in a model-checking framework. Dynamic systems are abstracted here as Discrete-Event Systems (DESs) and modeled by Input/Output Transition Systems (IOTSs). We reformulate diagnosability issues using CTL formula while considering extended definitions of diagnosability. Moreover, we introduce a formal definition of K-diagnosability in model-checking framework and we discuss the problem of K min-diagnosability (the minimal value of K ensuring diagnosability). We also show how diagnosability analysis in model-checking framework can be extended in order to deal with repeated/intermittent failures. In this regard, the case of [1-∞]-diagnosability analysis is investigated. Finally, some of these theoretical contributions are illustrated through a benchmark.
We propose in this paper a monitoring approach for Discrete Event Systems of which behavior is a-... more We propose in this paper a monitoring approach for Discrete Event Systems of which behavior is a-priori modelled. The model used to represent the system behaviour is Time Petri Net. Our approach proposes a set of mechanisms which exploit the temporal constraints on the bahaviour to fill up the partial observability on the system. This enables, on-line, tracking the system state and identifying the factual scenarios which occur on the system. That allows mainly detecting and identifying possible failures which can occur on the system. This kind of approaches is very suitable for railway safety studies, as the control view point behaviour can be easily represented by means of discrete event model. An illustration on a railway system is given throughout the paper to explain the various developed mechanisms.
We develop in this paper a diagnosis approach for Discrete Event Systems (DES) starting from a ti... more We develop in this paper a diagnosis approach for Discrete Event Systems (DES) starting from a time Petri net model representing the apriori known behavior of such a system. The originality of our approach lies in the combination made of the concept of event observability with the exploitation of the temporal constraints on these events in order to refine the result of the diagnosis process.
The work presented in this paper is part of a project that aims to develop of a new approach to t... more The work presented in this paper is part of a project that aims to develop of a new approach to time-constrained system verification based on UML. In fact, being relatively easy to learn and use, UML is very popular, unlike formal methods. Nevertheless, formal models provide developers with several advantages: they can be used for activities, such as properties verification, which are crucial for critical system development. Such activities are less effective when carried out on UML models. Also, because UML semantics is informal, the automatic verification of UML models is directly unfeasible. In this paper, we propose a new verification approach that takes advantage of UML Statecharts model to implement a new technique based on both Timed Automata Observers and model checking. The contributions of the paper are the definition of new time constraints (properties) taxonomy and the definition of a Statecharts patterns’ base. These patterns are then translated to Timed Automata Observ...
The paper deals with the Pansafer project which aims at improving safety at Level Crossings. This... more The paper deals with the Pansafer project which aims at improving safety at Level Crossings. This project integrates several tasks; First a fine statistical analysis is carried out using accidents/incidents data basis as well as several other sources. At the same time we lead a human behaviour study at LX area in order to determine potential risky behaviours. Then a functional model integrating all the elements in the LX area is established. This model will serve as a basis to point weak-points at the LX safety chain and to determine the potential improvements that have to be carried. The paper mainly focuses on two main technological solutions that potentially improve global safety at LX by anticipating and detecting risky situations and provide useful information able to prevent accidents. The first system is based on video surveillance and the second is a wireless communication system. The architecture of both systems are roughly discussed within this paper.
We develop in this paper a monitoring approach for Discrete Event Systems (DES) starting from a t... more We develop in this paper a monitoring approach for Discrete Event Systems (DES) starting from a time Petri net model representing the a priori known behavior of such a system. The originality of our approach lies in the combination made of the concept of event observability with the exploitation of the temporal constraints on these events in order to refine the result of the monitoring process.
International Journal of Soft Computing and Software Engineering, 2012
Systems' requirements are usually written in a natural language since it generally means a greate... more Systems' requirements are usually written in a natural language since it generally means a greater understanding among the various stakeholders. However, using an informal language potentially gives rise to interpretation problems, which are to be resolved prior to using (automated) verification techniques. This article tackles an important issue pertaining to requirement engineering: how to guide and help requirements' formalization? In order to support the formalization process, we propose a methodology based on a formal structure, which is the corner stone of the refinement process. The operating mode of the refinement process is highly iterative: the aforementioned structure is constructed incrementally until its validity is formally obtained. Although this process is formally backed up, it is a fundamentally subjective one, which means that interpretation errors can still occur. In case of errors, it is essential to be able to backtrack refinements until an interpretation error is found. This is why we require that each refinement be associated with a justification which may subsequently be analyzed in case an error occurred during the verification phase. This formalization process was designed to be used alongside an (unspecific) engineering process, in charge of the implementation. Once the formalization is complete, it is checked against the implementation using testing techniques, or directly against an implementation model via model-checking.
2016 13th International Workshop on Discrete Event Systems (WODES), 2016
In this paper, an approach to analyze diagnosability of intermittent failures in discrete-event s... more 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.
This paper deals with fault diagnosis of timed discrete event systems (TDESs), using a nondetermi... more This paper deals with fault diagnosis of timed discrete event systems (TDESs), using a nondeterministic model named labeled time Petri net (LTPN). Thanks to a skillful splitting of time intervals assigned to the LTPN transitions, analyzing diagnosability in such a timed context can be performed using techniques from the untimed context. Moreover, a deterministic structure called augmented state class set graph (ASG) is built on the fly, for both analyzing (∆-)diagnosability and deriving an online diagnoser.
ABSTRACT Système d'information (1) d'un usager à l'approche d'un ... more ABSTRACT Système d'information (1) d'un usager à l'approche d'un passage à niveau (3), caractérisé en ce qu'il comporte un dispositif d'information (2), monté au niveau d'un passage à niveau (3), et un équipement terminal de navigation (4) mobile, embarqué dans un véhicule (5) ou porté par un piéton, ledit dispositif d'information (2) comportant des moyens pour déterminer des données d'état dudit passage à niveau, et des moyens pour générer, à partir desdites données d'état, un message d'état du passage à niveau, ledit message d'état comportant en outre une géolocalisation dudit passage à niveau (3), ledit dispositif d'information (2) comportant des moyens de radiocommunication sans fil (10) aptes à transmettre ledit message d'état généré audit équipement terminal de navigation (4).
Dans cet article, nous présentons une approche qui permet de résoudre le problème de la Kdiagnost... more Dans cet article, nous présentons une approche qui permet de résoudre le problème de la Kdiagnosticabilité des réseaux de Petri (RdP) synchronisés et bornés. Tout d'abord, nous introduisons deux nouveaux concepts : la matrice d'incidence étendue qui intègre les informations relatives aux affectations des événements aux transitions, et le marquage étendu ainsi que l'équation d'état étendue, qui permet de transcrire le nombre d'occurrences de chaque événement depuis l'état initial, jusqu'à un certain marquage étendu cible. Sur la base de ces concepts, nous élaborons un nouvel algorithme d'analyse, à la volée, de la K-diagnosticabilité des RdP synchronisés partiellement observables. L'algorithme développé se base sur des procédures récursives et ne nécessite pas une construction a priori du graphe de marquage ni d'un diagnostiqueur.
Works in the field of verification systems have shown the critical importance of time. The nonsat... more Works in the field of verification systems have shown the critical importance of time. The nonsatisfaction of time may have important consequences for both security and performance points of view. For automated systems with level of security, the verification of time requirements is an essential part of the process validation system. In this paper, we are laying the foundations for a new and systematic approach for the verification of discrete event systems with time constraints. The contribution of this approach is threefold: first, unlike existing approaches, it allows for the verification of several requirements at once. Therefore, the approach is generic because we focus on developing mechanisms that take into account different types of requirements rather than the system to be verified. Finally, the implementation of the approach is almost as systematic because the verification tools we are developing are based on the instantiation of patterns. These patterns are designed on the basis of a classification of temporal requirements that we have established. The concepts of parallelism and hierarchy which characterize the Stocharts formalism compared to other state-transitions models help us build the foundations of our approach. An example of application to the control-command in the railway field is presented to illustrate the key concepts of our approach and its implementation.
The paper deals with monitoring experts' models in order to integrate them in a global reference ... more The paper deals with monitoring experts' models in order to integrate them in a global reference framework, which takes into account the different viewpoints relating to the design and exploitation of automated production systems. Metamodelling is used to obtain a single language of modelling and integration is used to obtain a single global model, which offers an overall coherent interpretation of the different viewpoints.
This work presents a method for verifying temporal requirements of time-constrained systems. The ... more This work presents a method for verifying temporal requirements of time-constrained systems. The method predates by establishing a new time constraints (properties) taxonomy. Then, a basis of observation patterns relative to the predefined requirements is developed. Our approach allows the automated verification of temporal requirements, initially expressed in a semi-formal formalism, through model transformation and modelchecking. The contributions of the paper are: the definition of a new time constraints (properties) typology as well as a basis of appropriate State Machines (SM) observation patterns. The second contribution consists in developing an algorithm for transforming UML SM with time annotations into Timed Automata (TA). In practice, in order to verify the temporal aspects of a given specification, the observation patterns relative to the investigated properties are instantiated to make appropriate observers. Then using our transformation algorithm, the system specification (denoted in the shape of an UML SM model) with time annotations as well as the obtained observers are translated into TA models. The TA system model is next synchronized with the TA observers. Thereby, the verification process is reduced to a reachability analysis.
This paper deals with analysis of diagnosability and K-diagnosability of dynamic systems in a mod... more This paper deals with analysis of diagnosability and K-diagnosability of dynamic systems in a model-checking framework. Dynamic systems are abstracted here as Discrete-Event Systems (DESs) and modeled by Input/Output Transition Systems (IOTSs). We reformulate diagnosability issues using CTL formula while considering extended definitions of diagnosability. Moreover, we introduce a formal definition of K-diagnosability in model-checking framework and we discuss the problem of K min-diagnosability (the minimal value of K ensuring diagnosability). We also show how diagnosability analysis in model-checking framework can be extended in order to deal with repeated/intermittent failures. In this regard, the case of [1-∞]-diagnosability analysis is investigated. Finally, some of these theoretical contributions are illustrated through a benchmark.
We propose in this paper a monitoring approach for Discrete Event Systems of which behavior is a-... more We propose in this paper a monitoring approach for Discrete Event Systems of which behavior is a-priori modelled. The model used to represent the system behaviour is Time Petri Net. Our approach proposes a set of mechanisms which exploit the temporal constraints on the bahaviour to fill up the partial observability on the system. This enables, on-line, tracking the system state and identifying the factual scenarios which occur on the system. That allows mainly detecting and identifying possible failures which can occur on the system. This kind of approaches is very suitable for railway safety studies, as the control view point behaviour can be easily represented by means of discrete event model. An illustration on a railway system is given throughout the paper to explain the various developed mechanisms.
We develop in this paper a diagnosis approach for Discrete Event Systems (DES) starting from a ti... more We develop in this paper a diagnosis approach for Discrete Event Systems (DES) starting from a time Petri net model representing the apriori known behavior of such a system. The originality of our approach lies in the combination made of the concept of event observability with the exploitation of the temporal constraints on these events in order to refine the result of the diagnosis process.
The work presented in this paper is part of a project that aims to develop of a new approach to t... more The work presented in this paper is part of a project that aims to develop of a new approach to time-constrained system verification based on UML. In fact, being relatively easy to learn and use, UML is very popular, unlike formal methods. Nevertheless, formal models provide developers with several advantages: they can be used for activities, such as properties verification, which are crucial for critical system development. Such activities are less effective when carried out on UML models. Also, because UML semantics is informal, the automatic verification of UML models is directly unfeasible. In this paper, we propose a new verification approach that takes advantage of UML Statecharts model to implement a new technique based on both Timed Automata Observers and model checking. The contributions of the paper are the definition of new time constraints (properties) taxonomy and the definition of a Statecharts patterns’ base. These patterns are then translated to Timed Automata Observ...
The paper deals with the Pansafer project which aims at improving safety at Level Crossings. This... more The paper deals with the Pansafer project which aims at improving safety at Level Crossings. This project integrates several tasks; First a fine statistical analysis is carried out using accidents/incidents data basis as well as several other sources. At the same time we lead a human behaviour study at LX area in order to determine potential risky behaviours. Then a functional model integrating all the elements in the LX area is established. This model will serve as a basis to point weak-points at the LX safety chain and to determine the potential improvements that have to be carried. The paper mainly focuses on two main technological solutions that potentially improve global safety at LX by anticipating and detecting risky situations and provide useful information able to prevent accidents. The first system is based on video surveillance and the second is a wireless communication system. The architecture of both systems are roughly discussed within this paper.
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