High-level Petri Nets Research Articles

A Knowledge Representation Environment for Manufacturing Control Systems Design and Prototyping

This paper presents some key ideas of a project on a design environment for manufacturing systems control. It is based on a tool hierarchy which integrates different techniques. The kernel is a knowledge representation language, called KRON, which embeddes three methodologies: frame based representation techniques, object oriented programming and High Level Petri Nets (HLPN). MIKRON, a manufacturing oriented tool, is built on top of KRON. A single model built using MIKRON can be used at different levels of a control hierarchy (coordination, scheduling and planning). It offers the graphic and formal expresion capacity of HLPN, as a mean of systematizing, formalizing the interconnection, synchronization and causal relations, as well as the information flow produced by the activity execution. Facilitates the integration of AI techniques for solving scheduling and planning problems. In addition, this tool supports the model execution and simulation.

STRUCTURED REPRESENTATION OF FMS INTEGRATING SI-NETS AND HIGH LEVEL PETRI NETS

In this paper a structured knowledge-based approach to the representation and scheduling of flexible manufactoring systems (FMSs) is described. Our approach is based on a structured conceptual representation (a KL-ONE-like Si-net representation formalism), extended with an instant-based temporal reasoning formalism. Furthermore, the approach integrates a particular extension to high-level Petri nets (PNs), structured timed colored Petri nets (STCPNs), for the modeling and simulation of the FMS. Such a representation scheme allows us to use SI-nets' good properties related to inference (classification and inheritance), which are lacking in PNs, and at the same time provides an extension toward an explicit representation for time. The integration of Si-nets with PNs is necessary because simulation and low-level coordination of FMSs require a procedural approach that is not within the aims of Si-nets. Therefore, procedural and symbolic levels, corresponding to the different hierarchical levels of the represe...

Automation System Design with High-Level Petri Nets: The PROTOB Environment

This paper presents PROTOB, an object-oriented CASE system based on an extended dataflow model defined using high level Petri nets, PROT nets. It consists of several tools supporting specification, modelling, prototyping and design activities within the framework of the operational software life cycle paradigm A case study concerning automatic warehousing systems is taken as application example of PROTOB.

Prototyping discrete part manufacturing systems

The paper presents a specification and prototyping language for manufacturing systems. The language is based on high-level Petri nets, is object oriented, is graphic with a textual part, and supports hierarchical decomposition: it is well suited for the description and simulation of complex, concurrent systems. The methodology that supports the language combines top-down and bottom-up approaches to achieve an executable description of a system, starting from an informal document and from well known objects taken from an application library.

Organization and information system design of manufacturing environments: the new M ∗ approach

Development of CIM systems requires models for enterprise and information system modelling and analysis, and tools and methods for database design. M ∗ methodology addresses these issues. In the paper, the new integrated high-level model of M ∗, based on high-level Petri-nets, for modelling engineering and manufacturing information systems is introduced. It allows description of an organization at two different levels (organization and conceptual) and, most importantly, description of, in an integrated way, both the organization behaviour and the manipulation actions on the database which support the information system activies. Moreover, the conceptual specification is executable.

Information system dynamics representation in production environments

This paper discusses the representation of dynamic features of an organization. The approach adopted is based on the use of high level Petri nets and allows the description of the system at two different levels: (a) the organization level, and (b) the conceptual level. The model is used as the description tool in a design methodology for developing the information system which supports the organization activity.

Specifying concurrent objects

The object-oriented style of programming (OOP) is gaining increasing importance as a practical technique for organizing large designs and programs. Another striking aspect of OOP is its potential f...

Concurrent system analysis using Petri nets: an optimized algorithm for finding net invariants

Analysis of net invariants has proved to be a powerful technique for investigating properties of concurrent systems modelled by generalized Petri nets. Unfortunately, the best known algorithms for invariant search have an exponential cost, leading in many real cases to unacceptable consumption of computing resources. An algorithm is presented here which, although still exponentially complex, introduces significant optimizations that are meant to considerably extend the practical feasibility of invariant analysis. After a short summary of the invariant method and a brief recall of existing algorithms, the features of the new algorithm are developed and proved. The optimizations proposed here could be successfully taken into account when designing new algorithms for high level Petri nets.

Stochastic high-level Petri nets and applications

A class of stochastic Petri nets called stochastic high-level Petri nets (SHLPNs) is proposed. SHLPNs are high-level Petri nets augmented with exponentially distributed firing times. SHLPNs generally lead to models with a smaller state space. A computer marking concept is introduced that allows a considerable reduction of the number of states and induces a correct grouping of states in the Markov-domain SHLPN models of multiprocessor systems. The main advantage of modeling homogeneous systems using SHLPNs is that the resulting models are simpler and more intuitive and have a smaller number of states, as shown by examples. >

PROTEAN: a high-level Petri net tool for the specification and verification of communication protocols

The PROTEAN protocol emulation and analysis computer aid is presented. It is based on a formal specification technique called numerical Petri nets (NPNs), and provides both graphical (color) and textual interfaces to the protocol designer. NPN specifications may be created, stored, appended to other NPNs, structured, edited, listed, displayed, and analyzed. Interactive simulation, exhaustive reachability analysis, and several directed graph analysis facilities are described. Specification languages are compared, with concentration on extended finite state machines and high-level Petri nets. Both the NPN and PROTEAN facilities are described and illustrated with a simple example. The application of PROTEAN to complex examples is mentioned briefly. Work towards a comprehensive protocol engineering workstation is also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Domain oriented analysis of PDE splitting algorithms

We consider the performance of Schwarz splitting algorithms for PDE problems on the hypothetical Multi- flex machine. The particular multi- flex considered consists of eight clusters of flex/32 multiprocessors. We introduce the concept of execution domains to model the three levels of memory on these machines: local, locally shared, and global. We apply the method of stochastic high level Petri nets (SHLPN) to model the performance of these PDE splitting algorithms on a Multi- flex machine. For very large, but realistic, applications we project potential speedup of 300 for 2D problems and more for 3D problems along with processor utilization of over 99 percent. Real computations on real machines can fall far short of this potential and still be very successful.

A graphical tool for the design and prototyping of distributed systems

This paper presents an approach of using modem graphical user interface techniques in the design and specification of complex distributed systems. A window-oriented and menu-driven net-editor and an integrated simulator with animation support have been implemented. This toolset is based on high-level Petri Nets, extended with an object-oriented paradigm and a hierarchical structuring facility. The flexibility and high level of abstraction support Rapid Prototyping.

An Introduction to High-Level Petri Nets

&lt;p&gt;This paper describes a Petri net model, where information is attached to each token and when a transition fires, it can inspect and modify the information. The model is based on predicate/transitions (Genrich and Lautenbach) and on coloured Petri nets (Jensen).&lt;/p&gt;&lt;p&gt;This generalization of ordinary Petri nets allows, for many applications, more manageable descriptions, due to the fact that equal subnets can be folded into each other yielding a much smaller net. The paper investigates how to analyse high-level Petri nets, and it turns out that invariants and reachability trees, two of the most important methods for ordinary Petri nets, can be generalized to apply for high-level Petri Nets.&lt;/p&gt;

Towards Reachability Trees for High-level Petri Nets

&lt;p&gt;High-level Petri nets have been introduced as a powerful net type, by which it is possible to handle rather complex systems in a succinct and manageable way. The success of high-level Petri nets is undebatable when we speak about description, but there is still much work to be done to establish the necessary analysis methods. It has already been shown how to generalize the concept of place-invariants and transition-invariants, from place-transition-nets to high-level Petri nets. Our present paper constitutes the first steps towards a generalization of reachability trees, which is one of the other important analysis methods known for PT-nets.&lt;/p&gt;&lt;p&gt;The central idea in our paper is the observation, that HL-nets often possess classes of equivalent markings. As an example an HL-net describing the five dining philo\-sophers has an equivalence-class consisting of those five markings in which exactly one philosopher is eating. These five markings are interchangeable, in the sense that their subtrees represent equivalent behaviours, where the only difference is the identity of the involved philosophers and forks. If we analyze one of these subtrees, we also understand the behaviour of the others.&lt;/p&gt;&lt;p&gt;We describe an algorithm which constructs the HL-tree. The algorithm can easily be automated and we will soon start the work on an implementation. The constructed HL-trees turn out to be considerably smaller than the corresponding PT-trees (reachability trees for the equivalent PT-nets).&lt;/p&gt;

Modeling production rules by Means of Predicate Transition networks

A formal tool, the PREDICATE TRANSITION networks, is proposed for representing rules in production systems. These networks have been introduced by Genrich and Lautenbach as a kind of high-level Petri nets. The peculiarity of such a formal tool lies in its well-formalized semantics, which can be described by means of an algebraic formalism and can be analyzed using the S-invariant method in order to prove properties of the network. A brief review of PREDICATE TRANSITION networks is followed by a description of their use in AI applications. In particular the characteristics which make them suitable for representing knowledge and control strategies in expert systems are analyzed.

Pascal Semantics by a Combination of Denotational Semantics and High-level Petri nets

This paper describes the formal semantics of a subset of PASCAL by means of a semantic model based on a combination of denotational semantics and high-level Petri nets. It is our intention that the paper be used as part of the written material for an introductory course in Computer Science.

High-Level Petri Nets

This paper combines two closely related net models, predicate/transition nets and coloured Petri nets, into a new net model called high-level Petri nets. The new model is intended to combine the qualities of the two old models into a single formalism, and we propose in the future to use high-level Petri nets instead of both predicate/transition nets and coloured Petri nets.

EPSILON: A System Description Language

&lt;p&gt;This paper presents the Epsilon language and defines its formal syntax and semantics. Epsilon is a language for the description of systems, which contain concurrent components, some of these being edp-equipment or by other means representing highly structured information handling. The actions consist of continuous changes described by equations, of communication between the components and of normal algorithmic actions.&lt;/p&gt;&lt;p&gt;Epsilon may be used for the description of computer systems together with their environments, e.g. production equipment and human operators. Parts of such a description may serve as the system specification from which computer programs are developed. Epsilon is not itself an implementable language.&lt;/p&gt;&lt;p&gt;This paper defines the semantics of Epsilon by means of a model based on high-level Petri nets, i.e. a model founded on the notion of concurrency. The model also uses denotational semantics and equation systems.&lt;/p&gt;

Formal Semantics by a Combination of Denotational Semantics and High-Level Petri Nets

&lt;p&gt;Denotational semantics has proved to be an excellent tool for the specification of nearly all kinds of declarations and commands in sequential languages, but the description of concurrent processes is in practice nearly impossible.&lt;/p&gt;&lt;p&gt;High-level Petri nets, on the other hand, have proved their value in the specification of communication and synchronization of concurrent processes.&lt;/p&gt;&lt;p&gt;We propose to combine the two models into a single approach, where denotational semantics is used to build up environments and to describe store transformations, while Petri nets are used to describe sequencing and communication.&lt;/p&gt;

System modelling with high-level Petri nets

The paper presents a high-level Petri net model of concurrent systems called predicate /transition-nets (PrT-nets). Its places represent variable properties of, or relations between, individuals; they are ‘predicates’ with variable extension. The transitions represent classes of elementary changes of those extensions. The model is introduced on the basis of a simple example from resource management. The central part of the paper is devoted to linear-algebraic techniques for verifying invariant assertions, yielding a calculus of S-invariants for PrT-nets. Finally, these modelling and analysis techniques are applied to a scheme for organizing a distributed data base taken from literature.