Workflow management promises a new solution to an age-old problem: controlling, monitoring, optimizing and supporting business processes. What is new about workflow management is the explicit representation of the business process logic which allows for computerized support. This paper discusses the use of Petri nets in the context of workflow management. Petri nets are an established tool for modeling and analyzing processes. On the one hand, Petri nets can be used as a design language for the specification of complex workflows. On the other hand, Petri net theory provides for powerful analysis techniques which can be used to verify the correctness of workflow procedures. This paper introduces workflow management as an application domain for Petri nets, presents state-of-the-art results with respect to the verification of workflows, and highlights some Petri-net-based workflow tools.

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The application of Petri-nets to workflow management

Business Process Management (BPM) includes methods, techniques, and tools to support the design, enactment, management, and analysis of operational business processes. It can be considered as an extension of classical Workflow Management (WFM) systems and approaches. Although the practical relevance of BPM is undisputed, a clear definition of BPM and related acronyms such as BAM, BPA, and STP are missing. Moreover, a clear scientific foundation is missing. In this paper, we try to demystify the acronyms in this domain, describe the state-of-the-art technology, and argue that BPM could benefit from formal methods/languages (cf. Petri nets, process algebras, etc.).

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Business process management: a survey

http://www.workflowpatterns.com/documentation/documents/yawl_qut_report_FIT-TR-2002-06.pdf

YAWL: yet another workflow language

Many of today's information systems are driven by explicit process models. Workflow management systems, but also ERP, CRM, SCM, and B2B, are configured on the basis of a workflow model specifying the order in which tasks need to be executed. Creating a workflow design is a complicated time-consuming process and typically there are discrepancies between the actual workflow processes and the processes as perceived by the management. To support the design of workflows, we propose the use of workflow mining. Starting point for workflow mining is a so-called "workflow log" containing information about the workflow process as it is actually being executed. In this paper, we introduce the concept of workflow mining and present a common format for workflow logs. Then we discuss the most challenging problems and present some of the workflow mining approaches available today.

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Workflow mining: a survey of issues and approaches

Based on a rigorous analysis of existing workflow management systems and workflow languages, a new workflow language is proposed: yet another workflow language (YAWL). To identify the differences between the various languages, we have collected a fairly complete set of workflow patterns. Based on these patterns we have evaluated several workflow products and detected considerable differences in their ability to capture control flows for non-trivial workflow processes. Languages based on Petri nets perform better when it comes to state-based workflow patterns. However, some patterns (e.g. involving multiple instances, complex synchronisations or non-local withdrawals) are not easy to map onto (high-level) Petri nets. This inspired us to develop a new language by taking Petri nets as a starting point and adding mechanisms to allow for a more direct and intuitive support of the workflow patterns identified. This paper motivates the need for such a language, specifies the semantics of the language, and shows that soundness can be verified in a compositional way. Although YAWL is intended as a complete workflow language, the focus of this paper is limited to the control-flow perspective.

Although workflow management emerged as a research area well over a decade ago, little consensus has been reached as to what should be essential ingredients of a workflow specification language. As a result, the market is flooded with workflow management systems, based on different paradigms and using a large variety of concepts. The goal of this paper is to establish a formal foundation for control-flow aspects of workflow specification languages, that assists in understanding fundamental properties of such languages, in particular their expressive power. Workflow languages can be fully characterized in terms of the evaluation strategy they use, the concepts they support, and the syntactic restrictions they impose. A number of results pertaining to this classification will be proven. This should not only aid those developing workflow specifications in practice, but also those developing new workflow engines.

/pdf/fundamentals-of-control-flow-in-workflows-3i0iswqfmp.pdf

Fundamentals of control flow in workflows

The goal of this paper is to demonstrate that process verification has matured to a level where it can be used in practice. Earlier techniques assumed simplified process models without the more advanced constructs available in today’s modelling languages (e.g., cancellation and OR-joins). This paper reports on new verification techniques that can be used to assess the correctness of real-life models. The proposed approach relies on using formal methods (i.e., mapping a business model to a reset net which is an extension of Petri nets, and performing state space analysis) to determine the correctness of business processes with cancellation and OR-joins. The paper also demonstrates how reduction rules can be used to improve the efficiency. We present these techniques in the context of the workflow language YAWL that provides direct support for 20 most frequently used patterns found today (including cancellation and OR-joins). But the results also apply to other languages with these features (e.g., BPMN, EPCs, UML activity diagrams, etc.). We have developed an editor that provides diagnostic information based on the techniques presented in this paper.

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Business process verification – finally a reality!

YAWL (Yet Another Workflow Language) workflow language supports the most frequent control-flow patterns found in the current workflow practice. As a result, most workflow languages can be mapped onto YAWL without the loss of control-flow details, even languages allowing for advanced constructs such as cancellation regions and OR-joins. Hence, a verification approach for YAWL is desirable, because such an approach could be used for any workflow language that can be mapped onto YAWL. Unfortunately, cancellation regions and OR-joins are 'non-local' properties, and in general we cannot even decide whether the desired final state is reachable if both patterns are present. This paper proposes a verification approach based on (i) an abstraction of the OR-join semantics; (ii) the relaxed soundness property; and (iii) transition invariants. This approach is correct (errors reported are really errors), but not necessarily complete (not every error might get reported). This incompleteness can be explained because, on the one hand, the approach abstracts from the OR-join semantics and on the other hand, it may use only transition invariants, which are structural properties. Nevertheless, our approach can be used to successfully detect errors in YAWL models. Moreover, the approach can be easily transferred to other workflow languages allowing for advanced constructs such as cancellations and OR-joins.

/pdf/verifying-workflows-with-cancellation-regions-and-or-joins-tjsr9causl.pdf

Verifying Workflows with Cancellation Regions and OR-joins: An Approach Based on Relaxed Soundness and Invariants

Workflow management systems facilitate the everyday operation of business processes by taking care of the logistic control of work. In contrast to traditional information systems, they attempt to support frequent changes of the workflows at hand. Therefore, the need for analysis methods to verify the correctness of workflows is becoming more prominent. In this paper we present a tool based on Petri nets: Woflan. Woflan (WOrkFLow ANalyzer) is an analysis tool which can be used to verify the correctness of a workflow procedure. The analysis tool uses state-of-the-art techniques to find potential errors in the definition of a workflow procedure.

A Petri-net-based Tool to analyze workflows

The Workflow Patterns provide a conceptual foundation for the control-flow, data and resource perspectives of process-aware information systems (PAIS). In this paper we present newYAWL, a reference language for PAIS based on the workflow patterns. newYAWL radically extends previous work undertaken on the YAWL language and provides a comprehensive formal description of how the complete set of workflow patterns can be realized and integrated in the context of an operational PAIS.

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van der Wmp Wil Aalst

Papers

Fundamentals of control flow in workflows

Business process verification – finally a reality!

Verifying Workflows with Cancellation Regions and OR-joins: An Approach Based on Relaxed Soundness and Invariants

A Petri-net-based Tool to analyze workflows

newYAWL : achieving comprehensive patterns support in workflow for the control-flow, data and resource perspectives