Construction of Occurrence Graphs with Permutation Symmetries Aided by the Backtrack Method

This paper recalls the concept of occurrence graphs with permuta- tion symmetries (OS-graphs) for Coloured Petri Nets. It is explained how so-called self-symmetries can help to speed up construction of OS- graphs. The contribution of the paper is to suggest a new method for calculation of self-symmetries, the Backtrack Method. The method is based on the so-called Backtrack Algorithm, which originates in com- putational group theory. The suggestion of the method is justified, both by identifying an important general complexity property and by obtaining encouraging experimental performance measures.Topics. Coloured Petri Nets, reduced state spaces, occurrence graphs with permutation symmetries, self-symmetries, computational group theory, backtrack searches

Analysing Coloured Petri Nets by the Occurrence Graph Method

This paper provides an overview og the work done for the author's PhD thesis. The research area of Coloured Petri Nets is introduced, and the available analysis methods are presented. The occurrence graph method, which is the main subject of this thesis, is described in more detail. Summaries of the six papers which, together with this overview, comprise the thesis are given, and the contributions are discussed.A large portion of this overview is dedicated to a description of related work. The aim is twofold: First, to survey pertinent results within the research areas of -- in increasing generality -- Coloured Petri Nets, High-level Petri Nets, and formalisms for modelling and analysis of parallel and distributed systems. Second, to put the results obtained in this thesis in a wider perspective by comparing them with important related work

Analysing Bang & Olufsen's BeoLink Audio/Video System Using Coloured Petri Nets

Bang & Olufsen A/S (B&O) is a renowned manufacturer of audio and video products. Their BeoLink (BeoLink) system distributes sound and vision throughout a home via a network. In this way, e.g., while doing the cooking in the kitchen, a person can remotely select and listen to a track from a CD, loaded in the CD player situated in the living room. To resolve conflicts, synchronisation between various actions is needed, and is indeed taken care of by appropiate communication protocols.The purpose of the project described in this paper vas to test Coloured Petri Nets (CP-nets or CPN) as a way to improve B&O's methods for specification, validation, and verification of protocols. In the main experiment, an engineer from B&O used the Desing/CPN tool to build a simulations with a familiar graphical feedback, and to formally verify crucial properties using occurrence graphs (also known as state spaces and reachability graphs/trees). The latter activity demonstrated the applicability of occurrence graphs for timed CP-nets. Moreover, CPN was used to examine important aspects of a possible future revision of Beo-Link, and to check compatibility between the new and the old version. Based on the experiments reported in this paper, CPN has been included in the set of methods for specification, validation, and verification of future protocols at B&O. Topics: System design oand verification using nets; higher-level net models; computer tools for nets; experience with using nets, case studies; application of nets to protocols and embedded systems

Modelling and Analysis of Distributed Program Execution in BETA Using Coloured Petri Nets

Recently, abstractions supporting distributed program execution in the object-oriented language BETA have been designed. A BETA object on one computer may invoke a remote object, i.e., an object hosted by another computer. In this project, the formalism of Coloured Petri Nets (CP-nets or CPN) is used to describe and analyse the protocol for remote object invocation. In the first place, we build a model in order to describe, understand, and improve the protocol. Remote object invocation in BETA is modelled on the level of threads (lightweight processes) with emphasis on the competition for access to critical regions and shared resources. Secondly, the model is analysed. It is formally proved that it has a set of desirable properties, e.g., absence of dead markings.Topics: Systemdesign and verfication using nets; higher-level nets models; computer tools for nets; experience with using nets, case studies; application of nets to protocols

A Case Study on Coloured Petri Nets in object-oriented analysis and design

Selected Papers of the Second International Workshop on Model-Based Methodologies for Pervasive and Embedded Software (MOMPES'05), June 6, 2005, Rennes, France.In this paper,we first demonstrate how a coloured Petri nets(CPN) model can be used to capture requirements for a considered example system, an elevator controller. Then, we show how this requirements-level CPN model is transformed into a design-level object-oriented CPN model, which is structurally and conceptually closer to class diagrams and object-oriented programming languages. The CPN models reduce the gap between user-level requirements and the respective implementation, thus simplifying the imple- mentation or code generation. Finally, we discuss the code generation from object-oriented CPN models

Computer Aided Verification of Lamport's Fast Mutual Exclusion Algorithm - Using Coloured Petri Nets and Occurrence Graphs with Symmetries

In this paper, we present a new computer tool for verification of distributed systems. As an example, we establish the correctness of Lamport's Fast Mutual Exclusion Algorithm. The tool implements the method of occurrence graphs with symmetries (OS-graphs) for Coloured Petri Nets(CP-nets). The basic idea in the approach is to exploit the symmetries inherent in many distributed systems to construct a condensed state space. We demonstrate a signigicant increase in the number of states which can be analysed. The paper is to a large extent self-contained and does not assume any prior knowledge of CP-nets (or any other kinds of Petri Nets) or OS-graphs. CP-nets and OS-graphs are not our invention. Our contribution is development of the tool and verification of the example.Index Terms: Modelling and Analysis of Distributed Systems, Formal Verification, Coloured Petri Nets, High-Level Petri Nets, Occurrence Graphs, State Spaces, Symmetries, Mutual Exclusion

Design/CPN - A Computer Tool for Coloured Petri Nets

In this paper, we describe the computer tool Design/CPN supporting editing, simulation, and state space analysis of Coloured Petri Nets. So far, approximately 40 man-years have been invested in the development of Design/CPN. It is used world-wide by more than 200 companies and research institutions. For the presentation, we draw from the experiences gained in recent industrial application using Coloured Petri Nets in the design, validation, and verification of communication protocols for audio/video systems

The Role of Plasma Extracellular Vesicles in Remote Ischemic Conditioning and Exercise-Induced Ischemic Tolerance

Ischemic conditioning and exercise have been suggested for protecting against brain ischemia-reperfusion injury. However, the endogenous protective mechanisms stimulated by these interventions remain unclear. Here, in a comprehensive translational study, we investigated the protective role of extracellular vesicles (EVs) released after remote ischemic conditioning (RIC), blood flow restricted resistance exercise (BFRRE), or high-load resistance exercise (HLRE). Blood samples were collected from human participants before and at serial time points after intervention. RIC and BFRRE plasma EVs released early after stimulation improved viability of endothelial cells subjected to oxygen-glucose deprivation. Furthermore, post-RIC EVs accumulated in the ischemic area of a stroke mouse model, and a mean decrease in infarct volume was observed for post-RIC EVs, although not reaching statistical significance. Thus, circulating EVs induced by RIC and BFRRE can mediate protection, but the in vivo and translational effects of conditioned EVs require further experimental verification