Cédric Favre

Instantaneous Soundness Checking of Industrial Business Process Models

We report on a case study on control-flow analysis of business process models. We checked 735 industrial business process models from financial services, telecommunications and other domains. We investigated these models for soundness (absence of deadlock and lack of synchronization) using three different approaches: the business process verification tool Woflan, the Petri net model checker LoLA, and a recently developed technique based on SESE decomposition. We evaluate the various techniques used by these approaches in terms of their ability of accelerating the check. Our results show that industrial business process models can be checked in a few milliseconds, which enables tight integration of modeling with control-flow analysis. We also briefly compare the diagnostic information delivered by the different approaches.

Analysis on demand: Instantaneous soundness checking of industrial business process models

We report on a case study on control-flow analysis of business process models. We checked 735 industrial business process models from financial services, telecommunications, and other domains. We investigated these models for soundness (absence of deadlock and lack of synchronization) using three different approaches: the business process verification tool Woflan, the Petri net model checker LoLA, and a recently developed technique based on SESE decomposition. We evaluate the various techniques used by these approaches in terms of their ability of accelerating the check. Our results show that industrial business process models can be checked in a few milliseconds, which enables tight integration of modeling with control-flow analysis. We also briefly compare the diagnostic information delivered by the different approaches and report some first insights from industrial applications.

A Fast Onboard Relative Positioning Module for Multirobot Systems

We present an onboard robotic module that can determine relative positions among miniature robots. The module uses high-frequency-modulated infrared emissions to enable nearby robots to determine the range, bearing, and message of the sender with a rapid update rate. A carrier sense multiple access protocol is employed for scalable operation. We describe a technique for calculating the range and bearing between robots, which can be generalized for use with more sophisticated relative positioning systems. Using this method, we characterize the accuracy of positioning between robots and identify different sources of imprecision. Finally, the utility of this module is clearly demonstrated with several robotic formation experiments, where precise multirobot formations are maintained throughout difficult maneuvers.

The relationship between workflow graphs and free-choice workflow nets

Workflow graphs represent the main control-flow constructs of industrial process modeling languages such as BPMN, EPC and UML activity diagrams, whereas free-choice workflow nets are a well understood class of Petri nets that possesses many efficient analysis techniques. In this paper, we provide new results on the translation between workflow graphs and free-choice workflow nets.We distinguish workflow graphs with and without inclusive Or-logic. For workflow graphs without inclusive logic, we show that workflow graphs and free-choice workflow nets are essentially the same thing. More precisely, each workflow graph and each free-choice workflow net can be brought into an equivalent normal form such that the normal forms are, in some sense, isomorphic. This result gives rise to a translation from arbitrary free-choice workflow nets to workflow graphs.For workflow graphs with inclusive logic, we provide various techniques to replace inclusive Or-joins by subgraphs without inclusive logic, thus giving rise to translations from workflow graphs to free-choice nets. Additionally, we characterize the applicability of these replacements. Finally, we also display a simple workflow graph with an inclusive Or-join, which, in some sense, cannot be replaced. This shows a limitation of translating inclusive logic into free-choice nets and illustrates also a difficulty of translating inclusive logic into general Petri nets.

Supporting different process views through a shared process model

Different stakeholders in the Business Process Management (BPM) life cycle benefit from having different views onto a particular process model. Each view can show, and offer to change, the details relevant to the particular stakeholder, leaving out the irrelevant ones. However, introducing different views on a process model entails the problem to synchronize changes in case that one view evolves. This problem is especially relevant and challenging for views at different abstraction levels. In this paper, we propose a Shared Process Model that provides different stakeholder views at different abstraction levels and that synchronizes changes made to any view. We present detailed requirements and a solution design for the Shared Process Model in this paper. Moreover, we also present an overview of our prototypical implementation to demonstrate the feasibility of the approach.

Symbolic execution of acyclic workflow graphs

We propose a new technique to analyze the control-flow, i.e., the workflow graph of a business process model, which we call symbolic execution. We consider acyclic workflow graphs that may contain inclusive OR gateways and define a symbolic execution for them that runs in quadratic time. The result allows us to decide in quadratic time, for any pair of control-flow edges or tasks of the workflow graph, whether they are sometimes, never, or always reached concurrently. This has different applications in finding control- and data-flow errors. In particular, we show how to decide soundness of an acyclic workflow graph with inclusive OR gateways in quadratic time. Moreover, we show that symbolic execution provides diagnostic information that allows the user to efficiently deal with spurious errors that arise due to over-approximation of the data-based decisions in the process.

Diagnostic Information for Control-Flow Analysis of Workflow Graphs a.k.a. Free-Choice Workflow Nets

A workflow graph is a classical flow graph extended by concurrent fork and join. Workflow graphs can be used to represent the main control-flow of e.g. business process models modeled in languages such as BPMN or UML activity diagrams. They can also be seen as compact representations of free-choice Petri nets with a unique start and a unique end. A workflow graph is said to be sound if it is free of deadlocks and exhibits no lack of synchronization, which correspond to liveness and safeness of a slightly modified version of the corresponding Petri net. We present a new characterization of unsoundness of workflow graphs in terms of three structural, i.e., graphical error patterns. We also present a polynomial-time algorithm that decides unsoundness and returns for each unsound workflow graph, one of the three structural error patterns as diagnostic information. An experimental evaluation on over 1350 workflow graphs derived from industrial business process models suggests that our technique performs well in practice.

The difficulty of replacing an inclusive OR-join

Some popular modeling languages for business processes, e.g., BPMN, contain inclusive OR-joins (IOR-joins), but others, e.g., Petri nets, do not. Various scenarios in Business Process Management require, or benefit from, translating a process model from one language to another. This paper studies whether the control flow of a process containing IOR-joins can be translated into a control flow without IOR-joins. First we characterize which IOR-joins can be replaced locally and define a local replacement for each replaceable IOR-join. Then, we present examples that cannot be locally replaced but have a more general translation. We give a non-local replacement technique, together with its condition of applicability, which runs in polynomial time. Finally, we show that there exist simple process models with an IOR-join that cannot be replaced --- in the sense that its synchronization behavior cannot be obtained by any combination of AND and XOR gateways. The proof reveals an intrinsic limitation on the replaceability of IOR-joins and hence the translatability of BPMN-like control flow into Petri nets.

Supporting different process views through a Shared Process Model

Different stakeholders in the business process management (BPM) life cycle benefit from having different views onto a particular process model. Each view can show, and offer to change, the details relevant to the particular stakeholder, leaving out the irrelevant ones. However, introducing different views on a process model entails the problem to synchronize changes in case that one view evolves. This problem is especially relevant and challenging for views at different abstraction levels. In this paper, we propose a Shared Process Model that provides different stakeholder views at different abstraction levels and synchronizes changes made to any view. We present detailed requirements and a solution design for the Shared Process Model. We also present an overview of our prototypical implementation to demonstrate the feasibility of the approach. Finally, we report on a comprehensive evaluation of the approach on real Business–IT modeling scenarios.