Inconsistency Management and View Updates

AbstractInconsistency management in component-based languages is the identification and resolution of conflicting constraints or expectations between the different components which make up a system. Here we present a category theoretical framework for detecting and classifying those inconsistencies which can arise throughout a simulation. In addition, the framework permits us to apply techniques developed for defining database view updates. With these, we can analyse the set of traces of a system with respect to a particular behaviour in a subsystem

The Consistent Use of Names and Polymorphism in the Definition of Object Petri Nets

: This paper seeks to present a more elegant and general definition of Object Petri Nets than previously. It is more general since it supports transition fusion as well as place fusion. It is more elegant because it captures all the notions of place substitution, transition substitution, place fusion, and transition fusion under the single notion of binding. This is achieved by explicitly supporting names in the formalism, in line with the p-calculus which recognises that names are pervasive and should be explicitly included in a formalism in order to model object mobility. The definition in this paper is also more consistent in its use of polymorphism and embodies a more obvious duality between states and changes of state. Object Petri Nets represent a complete integration of object-oriented concepts into Petri Nets. They have a single class hierarchy which includes both token types and subnet types, and which readily supports modelling systems with multiple levels of activity. Intera..

From Coloured Petri Nets to Object Petri Nets

ion Abstract: This paper seeks to establish within a formal framework how Coloured Petri Nets can be enhanced to produce Object Petri Nets. It does so by defining a number of intermediate Petri Net formalisms and identifying the features introduced at each step of the development. Object Petri Nets support a complete integration of object-oriented concepts into Petri Nets, including inheritance and the associated polymorphism and dynamic binding. In particular, Object Petri Nets have a single class hierarchy which includes both token types and subnet types. Interaction between subnets can be either synchronous or asynchronous depending on whether the subnet is defined as a super place or a super transition. The single class hierarchy readily supports multiple levels of activity in the net and the generation and removal of tokens has been defined so that all subcomponents are simultaneously generated or removed, thus simplifying memory management. Despite this descriptive power, Object..

On the Abstraction of Coloured Petri Nets

ion of Coloured Petri Nets Charles Lakos, Computer Science Department, University of Tasmania, GPO Box 252C, Hobart, TAS, 7001, Australia. Email: [email protected] Abstract: This paper considers the appropriate properties for abstract net components in the Coloured Petri Net formalism. In doing so, it attempts to maintain the duality between places and transitions which is so foundational to Petri Net theory. It also defines what it means to execute the net at an abstract level. Keywords: Theory of High-Level Petri Nets, Abstraction, Duality 1 Introduction A number of proposals have been made for abstraction and hierarchy constructs for Petri Nets (PTNs) in general, and Coloured Petri Nets (CPNs) in particular. Some of these emphasise conceptual issues, where the abstractions are used primarily to aid the process of developing a Petri Net model, but are subsequently discarded in the simulation or analysis of the model [18]. Some concentrate on the structural relationship ..

The Role of Substitution Places in Hierarchical Coloured Petri Nets

Hierarchical Coloured Petri Nets provide a powerful technique for modelling concurrent systems. The colouring of tokens avoids the need for unnecessarily duplicating the control structure of the net, as is the case for the simpler place/transition nets. The decomposition of complex nets is further encouraged by the provision of hierarchy constructs, whereby a subnet can be isolated as a separate page. It is common to find substitution transitions and place fusion sets implemented as the hierarchy constructs of coloured petri net tools. This paper examines the provision of substitution places and considers why this construct has not been more popular. It suggests an improved semantics for the construct to that originally proposed; it proposes a desirable extension; and it considers the contexts where this sort of construct would be most desirable. Kewords and phrases Coloured petri nets, object-oriented languages, encapsulation CR categories B.4.4, F.1.1 1 Introduction Coloured Pet..

Towards a Reflective Implementation of Object Petri Nets

: This paper presents the concept of<E-208> reflection, where a program modifies its own<E-198> interpretation. A number of applications of<E-208> reflection are examined and it becomes apparent<E-179> that the technique is particularly applicable to the<E-204> implementation of object-oriented languages. The<E-201> paper then considers how the technique can be<E-207> applied to the implementation of Object Petri Nets<E-198> (OPNs), a formalism for modelling concurrent,<E-167> object-oriented systems. It turns out that reflection<E-176> provides a simple and efficient implementation<E-147> scheme for the compositionality constructs of<E-208> OPNs. Further, it allows flexible scheduling<E-168> strategies to be employed in the simulation of<E-208> OPNs. 1 Introduction<E-12> Computational reflection has been of interest to<E-208> computer language researchers for a number of<E-208> years. It can be defined as the behaviour of a<E-212> reflective system, where a reflective system is a<E-..

Object Oriented Modelling with Object Petri Nets

: This paper informally introduces Object Petri Nets (OPNs) with a number of examples. OPNs support a thorough integration of object-oriented concepts into Petri Nets, including inheritance and the associated polymorphism and dynamic binding. They have a single class hierarchy which includes both token types and subnet types, thereby allowing multiple levels of activity in the net. The paper discusses some theoretical issues pertinent to the definition of OPNs, and compares the provisions of OPNs with those of other Concurrent Object-Oriented Programming Languages. The paper then considers a case study of using OPNs to model a cooperative editor for hierarchical diagrams. This extended example demonstrates the applicability of OPNs to the modelling of non-trivial concurrent systems. The methodology for deriving a Petri Net model is to adapt an object-oriented design methodology: the Object Model is prepared in Rumbaugh's OMT notation; the Dynamic Model is then prepared in the form of l..

The Object Orientation of Object Petri Nets

This paper informally introduces Object Petri Nets (OPNs) with a number of examples and discusses how this kind of Petri Net addresses a number of issues pertinent to Concurrent Object-Oriented Programming Languages. OPNs support a thorough integration of object-oriented concepts into Petri Nets, including inheritance and the associated polymorphism and dynamic binding. They have a single class hierarchy which includes both token types and subnet types, thereby allowing multiple levels of activity in the net. Yet OPNs retain the important property of being able to be transformed into behaviourally equivalent Coloured Petri Nets (CPNs), which can provide a foundation for adapting existing analysis techniques such as invariant analysis

A Cooperative Editor for Hierarchical Diagrams: An Object Petri Net Model

This paper presents a case study on the use of Object Petri Nets. The case study is that of a cooperative editor for hierarchical diagrams. The methodology for deriving the Petri Net model is to follow an object-oriented design methodology: first we prepare the Object Model in the OMT notation of Rumbaugh; then we prepare the Dynamic Model in the form of lifecycles, following the Shlaer-Mellor methodology; and finally we map these models into an Object Petri Net model. This approach has the advantage of guiding the development with well-accepted methodologies, but has the disadvantage of overlooking valid Petri Net solutions to the problem. As a result of this exercise, some loose ends in the Shlaer-Mellor methodology are identified and resolved, and a modification to the semantics of OPN super transitions is proposed. However, one overriding conclusion of this paper is that Object Petri Nets are suitable as a target formalism in such an object-oriented design methodology