Søren Christensen

The Petri net markup language: concepts, technology, and tools

The Petri Net Markup Language (PNML) is an XML-based interchange format for Petri nets. In order to support different versions of Petri nets and, in particular, future versions of Petri nets, PNML allows the definition of Petri net types. Due to this flexibility, PNML is a starting point for a standard interchange format for Petri nets. This paper discusses the design principles, the basic concepts, and the underlying XML technology of PNML. The main purpose of this paper is to disseminate the ideas of PNML and to stimulate discussion on and contributions to a standard Petri net interchange format.

The practitioner’s guide to coloured Petri nets

Coloured Petri nets (CP-nets or CPNs) provide a framework for the design, specification, validation, and verification of systems. CP-nets have a wide range of application areas and many CPN projects have been carried out in industry, e.g., in the areas of communication protocols, operating systems, hardware designs, embedded systems, software system designs, and business process re-engineering. Design/CPN is a graphical computer tool supporting the practical use of CP-nets. The tool supports the construction, simulation, and functional and performance analysis of CPN models. The tool is used by more than four hundred organisations in forty different countries – including one hundred commercial companies. It is available free of charge, also for commercial use. This paper provides a comprehensive road map to the practical use of CP-nets and the Design/CPN tool. We give an informal introduction to the basic concepts and ideas underlying CP-nets. The key components and facilities of the Design/CPN tool are presented and their use illustrated. The paper is self-contained and does not assume any prior knowledge of Petri nets and CP-nets nor any experience with the Design/CPN tool.

CPN tools for editing, simulating, and analysing coloured Petri nets

CPN Tools is a tool for editing, simulating and analysing Coloured Petri Nets. The GUI is based on advanced interaction techniques, such as toolglasses, marking menus, and bi-manual interaction. Feedback facilities provide contextual error messages and indicate dependency relationships between net elements. The tool features incremental syntax checking and code generation which take place while a net is being constructed. A fast simulator efficiently handles both untimed and timed nets. Full and partial state spaces can be generated and analysed, and a standard state space report contains information such as boundedness properties and liveness properties. The functionality of the simulation engine and state space facilities are similar to the corresponding components in Design/CPN, which is a widespread tool for Coloured Petri Nets.

Modular Analysis of Petri Nets

This paper shows how two of the most important analysis methods for Petri nets can be performed in a modular way. We illustrate our techniques by means of modular Place/Transitions nets (modular PT-nets) in which the individual modules interact via shared places and shared transitions. For place invariants we show that it is possible to construct invariants of the total modular PT-net from invariants of the individual modules. For state spaces, we show that it is possible to decide behavioural properties of the modular PT-net from state spaces of the individual modules plus a synchronization graph, without unfolding to the ordinary state space. The generalization of our techniques to high-level Petri nets is rather straightforward.

Coloured Petri Nets Extended with Place Capacities, Test Arcs and Inhibitor Arcs

In this paper we show how to extend Coloured Petri Nets (CP-nets), with three new modelling primitives—place capacities, test arcs and inhibitor arcs. The new modelling primitives are introduced to improve the possibilities of creating models that are on the one hand compact and comprehensive and on the other hand easy to develop, understand and analyse. A number of different place capacity and inhibitor concepts have been suggested earlier, e.g., integer and multi-set capacities and zero-testing and threshold inhibitors. These concepts can all be described as special cases of the more general place capacity and inhibitor concepts defined in this paper.

Coloured Petri Nets Extended with Channels for Synchronous Communication

This paper shows how Coloured Petri Nets (CP-nets) can be extended to support synchronous communication. We introduce coloured communication channels through which transitions are allowed to communicate complex values. Small examples show how channel communication is convenient for creating compact and comprehensive models.

A Sweep-Line Method for State Space Exploration

We present a state space exploration method for on-the-fly verification. The method is aimed at systems for which it is possible to define a measure of progress based on the states of the system. The measure of progress makes it possible to delete certain states on-the-fly during state space generation, since these states can never be reached again. This in turn reduces the memory used for state space storage during the task of verification. Examples of progress measures are sequence numbers in communication protocols and time in certain models with time. We illustrate the application of the method on a number of Coloured Petri Net models, and give a first evaluation of its practicality by means of an implementation based on the DESIGN/CPN state space tool. Our experiments show significant reductions in both space and time used during state space exploration. The method is not specific to Coloured Petri Nets but applicable to a wide range of modelling languages.

How traumatic is breast cancer? Post-traumatic stress symptoms (PTSS) and risk factors for severe PTSS at 3 and 15 months after surgery in a nationwide cohort of Danish women treated for primary breast cancer.

Background:The literature shows considerable between-study variation in the prevalence of post-traumatic stress symptoms (PTSS) among women with breast cancer. Our aim was, therefore, to explore the prevalence of and risk factors for cancer-related PTSS in a nationwide inception cohort of women treated for primary breast cancer.Methods:In all, 68% of all Danish women receiving surgery for primary breast cancer between October 2001 and March 2004 completed a questionnaire at 3 months post surgery (n=3343), which included the impact of event scale (IES). In all, 94% of the disease-free women also completed a follow-up questionnaire at 15 months post surgery. Data on pre-cancer demographic, socioeconomic, and psychiatric status were obtained from national registries. The Danish Breast Cancer Cooperative Group and surgical departments provided information on disease variables, treatment, and comorbidity.Results:At 3 months post surgery, 20.1% had IES total scores suggesting severe PTSS (⩾35), compared with 14.3% at 15 months. In all, 48% with severe PTSS at 3 months also had scores above the cutoff at 15 months. Main predictors of severe PTSS at 15 months were low social status, previous physical and mental illness, axillary lymph node involvement (>3), and reduced physical functioning (PF) at 3 months.Conclusion:The results confirm that receiving a breast cancer diagnosis can be a significant traumatic experience, and that many women experience persistent cancer-related PTSS. Low social status, poor health status, low levels of PF, and disease severity were found to be risk factors for severe PTSS.

CPN/Tools: A Post-WIMP Interface for Editing and Simulating Coloured Petri Nets

CPN/Tools is a major redesign of the popular Design/CPN tool from the University of Aarhus CPN group. The new interface is based on advanced, post-WIMP interaction techniques, including bi-manual interaction, toolglasses and marking menus and a new metaphor for managing the workspace. It challenges traditional ideas about user interfaces, getting rid of pull-down menus, scrollbars, and even selection, while providing the same or greater functionality. It also uses the new and much faster CPN simulator and features incremental syntax checking of the nets. CPN/Tools requires an OpenGL graphics accelerator and will run on all major platforms.

Effects of an expressive writing intervention on cancer-related distress in Danish breast cancer survivors: results from a nationwide randomized clinical trial

To examine the effects of an expressive writing intervention (EWI) on cancer‐related distress, depressive symptoms, and mood in women treated for early stage breast cancer.