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Soundness of Workflow Nets: Classification, Decidability, and Analysis
 ACCEPTED FOR PUBLICATION IN FORMAL ASPECTS OF COMPUTING
"... Workflow nets, a particular class of Petri nets, have become one of the standard ways to model and analyze workflows. Typically, they are used as an abstraction of the workflow that is used to check the socalled soundness property. This property guarantees the absence of livelocks, deadlocks, and ..."
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Cited by 21 (3 self)
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Workflow nets, a particular class of Petri nets, have become one of the standard ways to model and analyze workflows. Typically, they are used as an abstraction of the workflow that is used to check the socalled soundness property. This property guarantees the absence of livelocks, deadlocks, and other anomalies that can be detected without domain knowledge. Several authors have proposed alternative notions of soundness and have suggested to use more expressive languages, e.g., models with cancellations or priorities. This paper provides an overview of the different notions of soundness and investigates these in the presence of different extensions of workflow nets. We will show that the eight soundness notions described in the literature are decidable for workflow nets. However, most extensions will make all of these notions undecidable. These new results show the theoretical limits of workflow verification. Moreover, we discuss some of the analysis approaches described in the literature.
Synthesis of deadlock prevention supervisors using Petri nets
 IEEE Transactions on Robotics and Automation
, 2002
"... which may have uncontrollable and unobservable transitions, the deadlock prevention procedure presented here determines a set of linear inequalities on the PN markings. When the PN is supervised so that its markings satisfy these inequalities, the supervised net is proved to be deadlockfree for all ..."
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which may have uncontrollable and unobservable transitions, the deadlock prevention procedure presented here determines a set of linear inequalities on the PN markings. When the PN is supervised so that its markings satisfy these inequalities, the supervised net is proved to be deadlockfree for all initial markings that satisfy the supervision constraints. Deadlockfreedom implies that there will always be at least one transition that is enabled in the closedloop (supervised) system. The method is not guaranteed to ensure liveness, as it can be applied to systems that cannot be made live under any circumstances. However, for controllable and observable PNs it is shown that when the method ensures liveness as well, the liveness ensuring supervisor is least restrictive. Moreover, it is shown that the method is not restrictive even for PNs in which not all transitions can be made live. The procedure allows automated synthesis of the supervisors. I.
Soundness of resourceconstrained workflow nets
 In ICATPN
, 2005
"... Abstract. We study concurrent processes modelled as workflow Petri nets extended with resource constraints. We define a behavioural correctness criterion called soundness: given a sufficient initial number of resources, all cases in the net are guaranteed to terminate successfully, no matter which s ..."
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Abstract. We study concurrent processes modelled as workflow Petri nets extended with resource constraints. We define a behavioural correctness criterion called soundness: given a sufficient initial number of resources, all cases in the net are guaranteed to terminate successfully, no matter which schedule is used. We give a necessary and sufficient condition for soundness and an algorithm that checks it.
ProcessOriented Organization Modeling and Analysis Based on Constraints
"... This paper presents a formal framework for processoriented modeling and analysis of organizations. The high expressivity of a sorted predicate logic language L PR used for specifying processoriented models allows representing a wide range of processrelated concepts (e.g., tasks, processes, reso ..."
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This paper presents a formal framework for processoriented modeling and analysis of organizations. The high expressivity of a sorted predicate logic language L PR used for specifying processoriented models allows representing a wide range of processrelated concepts (e.g., tasks, processes, resources), their characteristics and relations over them, which are described in the paper. Furthermore, every organization is characterized by a set of structural and behavioral constraints expressed over its tasks and processes, which are classified in this paper. In the proposed framework these constraints form a logical theory T PR in L PR, i.e. a set of formulae in L PR. Then, a constructed processoriented model is correct iff it satisfies T PR. The techniques for establishing the correctness of a processoriented model are implemented and described in this paper. The introduced framework is a part of a general framework for organization modelling and analysis.
Ayed, R.: Uniform verification of workflow soundness
 Transactions of the Institute of Measurement and Control Journal
, 2010
"... The development of work processoriented applications in various domains leads to workflow systems where a large number of flow instances run concurrently. A challenging problem is to provide methods for the uniform verification of these parameterized workflows, ie, proving the soundness of the work ..."
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The development of work processoriented applications in various domains leads to workflow systems where a large number of flow instances run concurrently. A challenging problem is to provide methods for the uniform verification of these parameterized workflows, ie, proving the soundness of the workflow for any number of instances. In this paper, we show the ability of structure theory of Petri nets to conduct a uniform verification for large subclasses of parameterized workflow nets modelling control flow patterns associated with complex synchronization mechanisms, routing constructs and resource allocation constraints. We can take advantage of these results in domains where collaborative activities and competition for resources are preponderant such as agile manufacturing systems, web service applications or grid computing. Key words: soundness; structure theory of Petri nets; uniform verification; workflow nets. 1.
ProcessOriented Organization Modeling and Analysis
"... Abstract. This paper presents a formal framework for processoriented modeling and analysis of organizations. The high expressivity of a sorted predicate logic language used for specification allows representing a wide range of processrelated concepts (e.g., tasks, processes, resources), characteri ..."
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Abstract. This paper presents a formal framework for processoriented modeling and analysis of organizations. The high expressivity of a sorted predicate logic language used for specification allows representing a wide range of processrelated concepts (e.g., tasks, processes, resources), characteristics and relations, which are described in the paper. Furthermore, for every organization, structural and behavioral constraints on processrelated concepts can be identified. Some of them should always be fulfilled by the organization (e.g., physical world constraints), whereas others allow some degree of organizational flexibility (e.g., some domain specific constraints). An organizational model is correct if it satisfies a set of relevant organizational constraints. This paper describes automated formal techniques for establishing correctness of organizational models w.r.t. a set of diverse constraint types. The introduced framework is a part of a general framework for organization modeling and analysis. 1.
Soundness of Workflow Nets with an Unbounded Resource is Decidable ⋆
"... Abstract. In this work we consider modeling of workflow systems with Petri nets. A resource workflow net (RWFnet) is a workflow net, supplied with an additional set of initially marked resource places. Resources can be consumed and/or produced by transitions. We do not constrain neither the interme ..."
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Abstract. In this work we consider modeling of workflow systems with Petri nets. A resource workflow net (RWFnet) is a workflow net, supplied with an additional set of initially marked resource places. Resources can be consumed and/or produced by transitions. We do not constrain neither the intermediate nor final resource markings, hence a net can have an infinite number of different reachable states. An initially marked RWFnet is called sound if it properly terminates and, moreover, adding any extra initial resource does not violate its proper termination. An (unmarked) RWFnet is sound if it is sound for some initial resource. In this paper we prove the decidability of both marked and unmarked soundness for a restricted class of RWFnets with a single unbounded resource place (1dim RWFnets). We present an algorithm for computing the minimal sound resource for a given sound 1dim RWFnet. 1
Processoriented organisation modelling and analysis
 In: Enterprise Information Systems Journal
, 2008
"... This paper presents a formal framework for processoriented modelling and analysis of organisations. The high expressivity of the sorted predicate logic language used for specification allows representing a wide range of processrelated concepts (e.g. tasks, processes, resources), characteristics an ..."
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This paper presents a formal framework for processoriented modelling and analysis of organisations. The high expressivity of the sorted predicate logic language used for specification allows representing a wide range of processrelated concepts (e.g. tasks, processes, resources), characteristics and relations, which are described in the paper. Furthermore, for every organisation, structural and behavioural constraints on processrelated concepts can be identified. Some of them should always be fulfilled by the organisation (e.g. physical world constraints), whereas others allow some degree of organisational flexibility (e.g. some domain specific constraints). An organisational specification is correct if it satisfies a set of relevant organisational constraints. This paper describes automated formal techniques for establishing correctness of organisational specifications with respect to a set of diverse constraint types. The introduced framework is a part of a general framework for organisation modelling and analysis.
A Formal Framework for Organization Modeling and Analysis
 In Handbook of Research on MultiAgent Systems: Semantics and Dynamics of Organizational Models, V. Dignum, Ed. Information Science Reference
"... Abstract. This chapter introduces a formal framework for modeling and analys is of organizations. It allows representing and reasoning about all important aspects of artificial and human organizations structured in a number of views, including performanceoriented, processoriented, power and inter ..."
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Cited by 1 (0 self)
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Abstract. This chapter introduces a formal framework for modeling and analys is of organizations. It allows representing and reasoning about all important aspects of artificial and human organizations structured in a number of views, including performanceoriented, processoriented, power and interactionrelated aspects. The framework provides means to model formal (pre)defined organizational structures and dynamics, informal relations and behavior of organizational actors. The meaning attached to the modeling concepts is specified based on the literature from Social Science. Unlike many existing organization modeling approaches the proposed framework has formal foundations based on the ordersorted predicate logic which enables different types of analysis of organizational specifications of particular views and across views. The framework allows scalability of modeling and analysis of complex organizations, by considering them at different aggregation levels. Furthermore, the framework provides support for realtime management of organizational processes. The framework was applied in several case studies, one of which is discussed here.
DOI: AN ANALYTICAL METHOD FOR WELLFORMED WORKFLOW/PETRI NETS VERIFICATION: CLASSICAL SOUNDNESS
"... In this paper we consider workflow nets as dynamical systems governed by ordinary difference equations described by a particular class of Petri nets. Workflow nets are formal model of business processes. Wellformed business processes correspond to sound workflow nets. Even if it seems considered ne ..."
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In this paper we consider workflow nets as dynamical systems governed by ordinary difference equations described by a particular class of Petri nets. Workflow nets are formal model of business processes. Wellformed business processes correspond to sound workflow nets. Even if it seems considered necessary to require soundness of workflow nets, there exist business processes with conditional behavior that will not necessarily satisfy the soundness property. In this sense, we propose an analytical method for showing that a workflow net satisfies the classical soundness property using a Petri net. To show our statement we use the Lyapunov stability theory to tackle the classical soundness verification problem for a class of dynamical systems described by Petri nets. This class of Petri nets allows a dynamical model representation that can be expressed in terms of difference equations. As a result, applying Lyapunov theory the classical soundness property for workflow nets is solved showing that the Petri net representation is stable. We show that a finite and nonblocking workflow net satisfies the sound property if and only if its corresponding PN is stable, i.e., given the incidence matrix A of the corresponding PN there exists a Φ strictly positive m vector such that AΦ ≤ 0. The key contribution of the paper is the analytical method itself that satisfies part of the definition of the classical soundness requirements. The method is for practical applications, guarantees that anomalies can be detected without domain knowledge and can be easily implemented into existing commercial systems that do not support the verification of workflows. Validity of the proposed method is successfully demonstrated by application examples.