Showing papers on "Petri net published in 1990"

Synchronization and storage models for multimedia objects

Abstract: A technique is presented for the formal specification and modeling of multimedia composition with respect to intermedia timing. The proposed model is based on the logic of temporal intervals and timed Petri nets. A strategy is evinced for constructing a database schema to facilitate data storage and retrieval of media elements based on the temporal relationship established by the proposed modeling tool. An algorithm which allows the retrieval of media elements from the constructed database in a manner which preserves the temporal requirements of the initial specification is presented. Using the proposed model, the synchronization requirements of complex structures of temporally related objects can be easily specified. >

Knowledge representation using fuzzy Petri nets

Abstract: A fuzzy Petri net model (FPN) is presented to represent the fuzzy production rule of a rule-based system in which a fuzzy production rule describes the fuzzy relation between two propositions. Based on the fuzzy Petri net model, an efficient algorithm is proposed to perform fuzzy reasoning automatically. It can determine whether an antecedent-consequence relationship exists from proposition d/sub s/ to proposition d/sub j/, where d/sub s/ not=d/sub j/. If the degree of truth of proposition d/sub s/ is given, then the degrees of truth of proposition d/sub j/ can be evaluated. The formal description of the model and the fuzzy reasoning algorithm are shown in detail. The upper bound of the time complexity of the fuzzy reasoning algorithm is O(nm), where n is the number of places and m is the number of transitions. Its execution time is proportional to the number of nodes in a sprouting tree generated by the algorithm only generates necessary reasoning paths from a starting place to a goal place, it can be executed very efficiently. >

Deadlock prevention and deadlock avoidance in flexible manufacturing systems using Petri net models

Abstract: Deadlocks constitute an important issue to be addressed in the design and operation of FMSs. It is shown that prevention and avoidance of FMS deadlocks can be implemented using Petri net models. For deadlock prevention, the reachability graph of a Petri net model of the given FMS is used, whereas for deadlock avoidance, a Petri-net-based online controller is proposed. The modeling of the General Electric FMS at Erie, PA, is discussed. For such real-world systems, deadlock prevention using the reachability graph is not feasible. A generic, Petri-net-based online controller for implementing deadlock avoidance in such real-world FMSs is developed. >

Petri nets are moniods

Abstract: Petri nets are widely used to model concurrent systems. However, their composition and abstraction mechanisms are inadequate: we solve this problem in a satisfactory way. We start by remarking that place/transition Petri nets can be viewed as ordinary, directed graphs equipped with two algebraic operations corresponding to parallell and sequential composition of transitions. A distributive law between the two operations captures a basic fact about concurrency. New morphisms are defined, mapping single, atomic transitions into whole computations, thus relating system descriptions at different levels of abstraction. Categories equipped with products and coproducts (corresponding to parallel and nondeterministic compositions) are introduced for Petri nets with and without initial markings. Petri net duality is expressed as a duality functor, and several new invariants are introduced. A tensor product is defined on nets, and their category is proved to be symmetric monoidal closed. This construction is generalized to a large class of algebraic theories on graphs. These results provide a formal basis for expressing the semantics of concurrent languages in terms of Petri nets. They also provide a new understanding of concurrency in terms of algebraic structures over graphs and categories that should apply to other models besides Petri nets and thus contribute to the conceptual unification of concurrency.

Synthesis of feedback control logic for a class of controlled Petri nets

Abstract: An efficient solution is developed for a class of forbidden state problems for discrete event systems (DESs). DESs are considered which can be modeled as cyclic controlled marked graphs (CMGs), a special class of controlled Petri nets (CPNs). The distributed representation of the DES state in terms of the CMG marking permits an efficient specification of the forbidden states in terms of individual place markings. More important, it is shown that the graphical representations of the state transition logic in a CMG can be used to synthesize state feedback logic which is maximally permissive while guaranteeing the forbidden states will not occur. The practical application of the theoretical results is illustrated for an example of automated guided vehicle (AGV) coordination in a flexible manufacturing facility. >

Specification and Verification of Concurrent Systems

Abstract: 1. The Interplay of Theory and Practice in a Parallel Object-Oriented Language.- 2. Object-Oriented Process Specification.- 3. Formal Object Oriented Specification of Distributed Systems.- 4. The Design and Development of Ada Real-Time Embedded Systems.- 5. Protocol Analysis and Implementation using NPNs and SDL.- 6. A Tool for the Performance Analysis of Concurrent Systems.- 7. Winston: A Tool for Hierarchical Design and Simulation of Concurrent Systems.- 8. A Specification-Verification Framework for Distributed Applications Software.- 9. Dynamic Communication Links.- 10. Formal Environment and Tools Description for the Analysis of Real Time Concurrent Systems.- 11. An Equivalence Decision Problem in Systolic Array Verification.- 12. Should Concurrency be Specified?.- 13. Semantics for Specifying Real-Time Systems (extended abstract only).- 14. Specifying Processes in Terms of their Environments.- 15. Hennessy-Milner Logic with Recursion as a Specification Language, and a Refinement Calculus based on It.- 16. A Functional Programming Approach to the Specification and Verification of Concurrent Systems.- 17. Synchronization in Network Protocols.- 18. From Synchronous to Asynchronous Communication.- 19. Formal Specification and Verification of Asynchronous Processes in Higher-Order Logic.- 20. Temporal Specifications Directed by Grammar and Design of Process Networks.- 21. Analysis of Estelle Specifications.- 22. Concurrency in Modula-2: Properties of the Language Primitives.- 23. Specification and Implementation of Concurrent Systems using PARLOG.- 24. Specification and Verification in Communications Standards.- 25. Experience with LOTOS and Environment LOTTE on an ISDN Protocol.- 26. The Specification and Design of a Nondeterministic Data Structure Using CCS.- 27. A High-Level Petri Net Specification of the Cambridge Fast Ring M-Access Service.- Poster Sessions.- 1. Modelling of Distributed Problem Solving using Logic Modified Petri Nets.- 2. An Animator for CSP Implemented in HOPE.- 3. A Concurrent Approach to the Towers of Hanoi.- Author Index.

Combinatorics on Traces

Abstract: Free partialy commutative monoids.- Recognizable and rational trace languages.- Petri nets and synchronization.- Complete semi-thue systems and mobius functions.- Trace replacement systems.

Partial (set) 2-structures. Part II: state spaces of concurrent systems

Abstract: The problem of characterizing state spaces of basic classes of Petri nets, and the problem of synthesizing state spaces of basic classes of Petri nets from their «abstract» descriptions in the form of directed edge-labeled graphs are investigated

Stochastic Petri net models of polling systems

Abstract: Finite population and finite capacity polling systems are considered. The behavior of these systems is described by means of generalized stochastic Petri nets. The exact results for the mean response times are obtained numerically by means of a stochastic Petri net package. Finite population polling systems are generally difficult to analyze. The results obtained can be used to validate approximate solutions to the above class of polling systems when such solutions become available. >

Performance evaluation of automated manufacturing systems using generalized stochastic Petri nets

Abstract: Generalized stochastic Petri net (GSPN) modules are used as basic building blocks to model and analyze complex manufacturing systems. This modular approach facilitates model construction and helps manage the complexity of modeling large manufacturing systems. The structural analysis ensures that the model is live and bounded, which guarantees that the equivalent Markov chain (MC) is ergodic. The temporal analysis is used to derive performance measures such as average production rates and average in process inventories. The main advantage of Petri nets (PNs) over MCs is that the number of places and transitions increases only slightly as the manufacturing system complexity increases, whereas the number of states in the MC increases exponentially. In addition, there is no need to enumerate all the possible states manually since they are automatically generated from the GSPN model. As a result, PN models can still be easily obtained for complicated interconnected systems. The straightforward application of this approach is demonstrated and reviewed for several manufacturing case studies. For serial transfer lines it is proven that this modular approach results in live and bounded GSPN models. Comparisons are made with deterministic and reduced state-space models. Examples containing as many as 9614 states are presented. >

Real-time system design

Abstract: Part I: Real-Time Issues. Time Handling. Objects. Adding Time to Objects. Part II: Real-Time Applications. Real-Time System Life Cycle. Structured Design Approaches. Petri Net Models. Axiomatic Approaches. Language Support and Restrictions. Verification and Validation of Real-Time Software. Part III: Real-Time Operating Systems. Allocation and Scheduling. Verification of Schedulability. Resource Allocation. Communication. Part IV: Operating System Implementation. The Maruti Operating System. Operational Issues and Examples. Part V: Epilog. 1990 ISE 544pp

Refinement of actions in causality based models

Abstract: We consider an operator for refinement of actions to be used in the design of concurrent systems. Actions on a given level of abstraction are replaced by more complicated processes on a lower level. This is done in such a way that the behaviour of the refined system may be inferred compositionally from the behaviour of the original system and from the behaviour of the processes substituted for actions. We define this refinement operation for causality based models like event structures and Petri nets. For Petri nets, we relate it to other approaches for refining transitions.

On the hierarchical modeling analysis and simulation of flexible manufacturing systems with extended Petri nets

Abstract: A class of Petri nets, called extended Petri nets, with multiple types of places, multiple classes of tokens and multiple arcs is proposed. It is utilized for the hierarchical modeling of flexible manufacturing systems, ensuring a priori that the extended Petri net system model obtained is live, bounded, consistent and error free. The proposed method views the operation of the flexible manufacturing system as a process that is decomposed into operations with specified precedence relations. For each operation the required resources are identified, and on the basis of these requirements the overall system is decomposed into a set of finite subsystems. The operation of each subsystem is modeled as an event graph representing a single resource activity cycle. The extended Petri net system model is synthesized from these component nets using certain synthesis rules. A software package has been developed to simulate the execution of the model obtained. >

The Mathematics of Petri Nets

Abstract: Petri-nets and vector addition systems graphs and ordered sets rational subsets in a monoid and semi-line sets vectors addition systems with states chains and reachability complements.

Models of discrete event dynamic systems

Abstract: Many new techniques for modeling discrete event dynamic systems have been developed in recent years; among them are Markov processes and their imbedded Markov chains, Petri nets, queuing networks, automata and finite-state machines, finitely recursive processes, min-max algebra models, and discrete event simulation and generalized semi-Markov processes. The authors demonstrate the main features of these models by applying them to a simple example and briefly compare their features. >

Reduction and covering of infinite reachability trees

Abstract: We present a structure for transition systems with which the main decidability results on Petri nets can be generalized to structured transition systems We define the reduced reachability tree of a structured transition system; it allows one to decide the finite reachability tree problem (also called the finite termination problem) and the finite reachability set problem A general definition of the coverability set is given and the procedure of Karp and Miller is extended for well-structured transition systems We show then that the coverability problem is a decidable problem in the framework of well-structured transition systems Finally, we introduce structured set of terminal states and we show that the finite reachability tree problem and the finite reachability set problem are decidable Coverability is an open problem for structured transition systems with a structured set of terminal states

Decidability of a temporal logic problem for petri nets

Abstract: The paper solves an open problem from [4] by showing a decision algorithm for a temporal logic language L ( Q ′, GF). It implies the decidability of the problem of the existence of an infinite weakly fair occurence sequence for a given Petri net; thereby an open problem from [2] is solved.

Flow Event Structures and Flow Nets

Abstract: In this paper we investigate the relationships between two models for concurrent computations, namely Petri nets and Winskel's event structures. A distinctive feature of these models, with respect to transition systems used in the so-called interleaving semantics, is that they provide an adequate account of the causa/relations between events in a distributed system. At least this is true for event structures, if not as clear for Petri nets. For instance in the net

Petri net objects for the design, validation and prototyping of user-driven interfaces

Abstract: Petri Net Objects (P.N.O.) are a high-level, object-structured dialect of Petri nets, primarily devised for the design of parallel systems. We show how this formalism can be used for the specification and design of event-driven interfaces, through the use of a real-life example. We then discuss the potential for dialogue validation, integration in UIMS and prototyping offered by this model.

Project Engineering: Computer-Oriented Planning and Operational Decision Making

Abstract: Manufacturing processes, scientific experiments, research programs, tax collection systems, are all endeavors once born as projects Project engineering is the application of science to the development and analysis of project plans, and to the supervision of their realization This book is a unified treatise on the technology of project planning and execution It provides a systematic understanding of the different methodological approaches to the development and supervision of project plans Readers are given a technical introduction to the main methodologies, such as graphs, activity networks, CPM, PERT, GERT, and Petri nets, and given guidance as to when and why to apply one technique rather than another The book deliberately emphasizes those techniques which are particularly suitable to exploiting the power of computation, and therefore supplies a solid platform for applying computer tools to the analysis and control of projects The book also introduces ODM, a methodology based on the theory of fuzzy sets for supporting plan execution supervisors in making operational choices The book is self-contained It is designed to serve professionals and students in the fields of systems engineering, computer aided planning, and decision support systems

Verifying temporal properties of processes

Abstract: Many interesting concurrent systems have infinite state spaces: examples include concurrent while programs; Petri Nets; CCS (or CSP) processes with value passing. All of these examples can be interpreted operationally as infinite labelled transition systems, structures of the form (7 ~, { --% : a E L }) where 7 ~ is a set of points (states, markings, processes) and % the appropriate binary transition relation on 7 ~ for each label a (action, set of events) belonging to the family L. A very rich temporal logic for expressing properties of such transition systems is a slight extension of the modal mu-calculus [9, 6] where the modalities are indexed by families of labels instead of individual labels. The question we address in this paper is: can model checking techniques, as introduced in [3] be extended from finite to infinite state spaces? (Pragmatically, this means moving from automated to computer-aided verification techniques.) We provide an affirmative answer by presenting a sound and complete tableau system for proving temporal properties of states (processes or markings) in arbitrary infinite transition system models. The tableau system extends local model checking techniques as presented in [4, 7, 11, 14]. The delicate aspect is showing that a point (or set of points) has, or lacks, a least fixed point property (a liveness property). The tableau proof system is data independent and therefore generalizes standard methods commonly used in program logics (such as Hoaxe logics). The verification technique is illustrated on examples drawn from CCS [8]. See [1] for the application of the method to Petri Nets and [12] for its application to concurrent while programs. Section 2 provides examples of CCS processes and their properties. In section 3 the syntax and semantics of the (slightly extended) modal mu-calculus are described. The tableau proof system is presented in section 4, and finally we briefly examine applications in section 5.

Computer-aided generation of programs modelling complex systems using colored petri nets

Abstract: A method and system in which a programmed digital computer serving as a graphical "engine" is employed to construct an executable model for a complex system using a hierarchy of so called "Colored" Petri nets (CPN's or CP-nets) The operation of the complex system is specified in terms of a graphical net structure and formal net inscriptions, such as arc expressions and guards, which ensure development of a program, or executable model, and associated data structures, properly defining the system Sophisticated syntax checks and other tools are provided for ensuring that the model so constructed conforms to a set of rules which guarantee valid system behavior

Formal analysis of the alternating bit protocol by temporal Petri nets

Abstract: Temporal Petri nets are Petri nets in which certain restrictions on the firings of transitions are represented by formulas containing temporal operators. The use of temporal Petri nets for formal specification and verification of the alternating bit protocol is discussed. The temporal Petri net which models the protocol is analyzed formally using the existing theory of omega -regular expressions and Buchi-automata. >

Design and implementation of a Petri net based toolkit for Ada tasking analysis

Abstract: The use of Petri nets for defining a general static analysis framework for Ada tasking is advocated. The framework has evolved into a collection of tools that have proven to be a very valuable platform for experimental research. The design and implementation of tools that make up the tasking-oriented toolkit for the Ada language (TOTAL) are defined and discussed. Modeling and query/analysis methods and tools are discussed. Example Ada tasking programs are used to demonstrate the utility of each tool individually as well as the way the tools integrate. TOTAL is divided into two major subsystems, the front-end translator subsystem (FETS) and the back-end information display subsystem (BIDS). Three component tools that make up FETS are defined. Examples demonstrate the way these tools integrate in order to perform the translation of Ada source to Petri-net format. The BIDS subsystem and, in particular, the use of tools and techniques to support user-directed, but transparent, searches of Ada-net reachability graphs are discussed. >

Top-down synthesis of live and bounded free choice nets

Abstract: The paper provides a set of rules for the stepwise synthesis of all and only live and bounded Free Choice nets. The starting point are nets composed by a circuit containing one place and one transition.

Temporal hyperprogramming

Abstract: The visual programming aspects of Trellis hypertext documents are described. A hypertext is a non-linearly organized, browsable information structure. The importance of browsing distinguishes hypertext from other network information systems. The possible experiences a user may have when interacting with a hypertext are as important as its form. Further, these browsing semantics should be an inherent characteristic of a document, not of the implementation that allows browsing. In essence, a hypertext is an active entity that has a visible behavior, not a static entity that is manipulated by external means. The Trellis model employs the dual nature of Petri nets to formally express both aspects of a hypertext in one structure. A Petri net is a bipartite graph, so it captures the linked structure of relationships among information elements. It is also an automaton, having an execution state and state transition rules, thereby formally capturing the interactions between reader and document. In this report, we define the temporal semantics of the Trellis model and illustrate them with a prototype hypertext system called @aTrellis. This environment joins timed events and active computing engines into a dynamic, parallel browsing structure. In @aTrellis, hypertext authoring is visual programming for a temporally-synchronized, visual outcome-temporal hyperprogramming.