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 typed communication channels through which transitions are allowed to communicate. Small examples show how channel commnunication is convenient for creating compact and comprehensive models. The concepts introduced in this paper originate from the practical use of Petri nets for modelling, and they are formally defined in such a way that they preserve the basic properties of CP-nets. We show how a CP-net with channels can be transformed into a behaviourally equivalent CP-net. This allows us to deduce properties of CP-nets with channels from well-known properties of CP-nets.As an example,we extend the concept of place invariants to cope with CP-nets with channels and show how place invariants can be found. This is done without transforming the CP-nets with channels into their equivalent CP-nets. CP-nets with channels can be used as a basis for new hierarchy constructs, and we outline an alternative to invocation transitions, based on CP-nets with channels. The reader is assumed to be familiar with the notion of CP-nets

Petri net based development of globally-asynchronous locally-synchronous distributed embedded systems

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresA model-based development approach (MBDA) for Globally-Asynchronous Locally- Synchronous (GALS) Distributed Embedded Systems (DESs) is proposed. This approach relies on the GALS-DESs specification through (low- or high-level) Petri net classes, which ensure that the created models are GALS, locally deterministic, distributable, networkindependent, and platform-independent and support their simulation, verification, and implementation (using simulation, model-checking, and code generation tools). The use of network- and platform-independent models enable the use of heterogeneous communication networks to support the distributed components interaction and enable the use of heterogeneous platforms to support the components and the communication nodes implementation. To enable the proposed MBDA, Petri nets are extended with a set of the concepts, most notably time-domains and asynchronous-channels. Algorithms to support the verification of GALS-DES models and their decomposition into implementable sub-models are also proposed. A tool chain framework (IOPT-tools) was extended with this work proposals, supporting their validation and the GALS-DESs development.Fundação para a Ciência e a Tecnologia - grant ref. SFRH/BD/62171/200

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

On Modelling Communication in Ubiquitous Computing Systems using Algebraic Higher Order Nets

Ubiquitous computing systems (UCSs) are designed to participate almostimperceptibly in everyday life. To ensure a solid operation, a UCS heavily depends on a reliable and efficient communication between its distributed computing components. Moreover components can join and leave the system at any time.In order to guarantee high quality systems, the use of models is inevitable especiallyat an early stage of the development process where models are the only possibilityto address a system which does not yet exist in reality. Petri nets and graph transformationsystems are established, theoretically well-founded concepts for modellingand analysing complex systems.This paper presents a formal approach for modelling core aspects of the communicationin UCSs by using Algebraic Higher Order Nets with Individual Tokens andgraph transformation. The approach is suitable to cover the different aspects ofcommunication and enables the analysis of specific properties. The approach and itssuitability are illustrated based on a running example. The feasibility of embeddingthe approach in a broader context of modelling is demonstrated in applying it to areal world system: the Living Place Hamburg

Augmenting High-Level Petri Nets to Support GALS Distributed Embedded Systems Specification

Part 9: Embedded Systems and Petri NetsInternational audienceHigh-level Petri net classes are suited to specify concurrent processes with emphasis both in control and data processing, making them appropriate to specify distributed embedded systems (DES). Embedded systems components are usually synchronous, which means that DES can be seen as Globally-Asynchronous Locally-Synchronous (GALS) systems. This paper proposes to include in high-level Petri nets a set of concepts already introduced for low-level Petri nets allowing the specification of GALS systems, namely time domains, test arcs and priorities. Additionally, this paper proposes external messages and three types of (high-level) asynchronous communication channels, to specify the interaction between distributed components based on message exchange. With these extensions, GALS-DES can be specified using high-level Petri nets. The resulting models include the specification of each component with well-defined boundaries and interface, and also the explicit specification of the asynchronous interaction between components. These models will be used not only to specify the system behavior, but also to be the input for model-checking tools (supporting its verification) and automatic code generation tools (supporting its implementation in software and hardware platforms), giving a contribution to the model-based development approach and hardware-software co-design of DES based on high-level Petri nets

Petri net model decomposition - a model based approach supporting distributed execution

Dissertação apresentada para obtenção do Grau de Doutor em Engenharia Electrotécnica, Especialidade de Sistemas Digitais, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaModel-based systems development has contributed to reducing the enormous difference between the continuous increase of systems complexity and the improvement of methods and methodologies available to support systems development. The choice of the modeling formalism is an important factor for success-fully increasing productivity. Petri nets proved to be a suitable candidate for being chosen as a system specification language due to their natural support of modeling processes with concurrency, synchronization and resource sharing, as well as the mechanisms of composition and decomposition. Also having a formal representation reinforces the choice, given that the use of verification tools is fundamental for complex systems development. This work proposes a method for partitioning Petri net models into concurrent sub-models, supporting their distributed implementation. The IOPT class (Input-Output Place Transition) is used as a reference class. It is extended by directed synchronous communication channels, enabling the com- munication between the generated sub-models. Three rules are proposed to perform the partition, and restrictions of the proposed partition method are identified. It is possible to directly compose models which result from the partitioning operation, through an operation of model addition. This allows the re-use of previously obtained models, as well as the easy modification of the intended system functionalities. The algorithms associated with the implementation of the partition operation are presented, as well as its rules and other procedures. The proposed methods are validated through several case studies emphasizing control components of automation systems

A phenomenal basis for hybrid modelling

This work in progress extends the new mechanical philosophy from science to engineering. Engineering is the practice of organising the design and construction of artifices that satisfy needs in real-world contexts. This work shows how artifices can be described in terms of their mechanisms and composed through their observable phenomena. Typically, the engineering of real system requires descrip- tions in many different languages: software components will be described in code; sensors and actuators in terms of their physical and electronic characteristics; plant in terms of differ- ential equations, perhaps. Another aspect of this work, then, to construct a formal framework so that diverse description languages can be used to characterise sub-mechanisms. The work is situated in Problem Oriented Engineering, a design theoretic framework engineering defined by the first two authors

Structured Performance Analysis for Component Based Systems

International audienceThe Component Based System (CBS) paradigm is now largely used to design software systems. In addition, performance and behavioural analysis remains a required step for the design and the construction of efficient systems. This is especially the case of CBS, which involve interconnected components running concurrent processes. % This paper proposes a compositional method for modeling and structured performance analysis of CBS. Modeling is based on Stochastic Well-formed Nets (SWN), a high level model of Stochastic Petri nets, widely used for dependability analysis of concurrent systems. Starting from the definition of the system given in a suitable Architecture Description Language, and from the definition of the elementary components, we build an SWN of the global system together with a set of SWNs modeling the components of the CBS and their connections. From these models, we derive performances of the system thanks to a structured analysis induced by the structure of the CBS. We describe the application of our method through an example designed in the framework of the CORBA Component Model