[PNtalk]
PNtalk System


PNtalk is a concurrent object oriented language based on high-level Petri nets and inspired by Smalltalk. It is an experimental language intended for formal specifications, simulation modelling and programming. PNtalk system is a computer tool designed to support the use of object oriented Petri nets connected to the language PNtalk.

In fact, the PNtalk system is an additional tool incorporated into the VisualWorks environment. This environment allows you to write Smalltalk classes, create graphical interfaces, communicate with databases etc. All these features can be used from the object oriented Petri nets as well. Nevertheless, it is of course possible to work with Petri nets only. In this case, the VisualWorks system is used only for launching the PNtalk system.


PNtalk system can be started from the modified VisualWorks Smalltalk Launcher.

The system consists of:
  • PNtalk Launcher from which all other tools are being started and which contains an area for displaying system messages.
  • PNtalk Browser which is intended for creating and editing object oriented Petri nets (OOPNs).
  • PNtalk Debugger which can be used for step-by-step investigating OOPNs evolution.
    • The users can choose from among several differrent modes of simulation (interactive token game, fast simulation, ...).


    The PNtalk system is provided freely in the form of a gzipped image for the ParcPlace (or under the new name ObjectShare) VisualWorks Smalltalk 2.0 object engine. Due to the fact that PNtalk is implemented in a Smalltalk environment, it can be used at all platforms for which the Smalltalk object engine is available, i.e. SUN with Solaris, PC with Windows 95 or Windows NT, ... Unfortunatelly, PNtalk is in the early stage of its development and therefore it is not completely stable and reliable - please be tolerant. If you are interested in the PNtalk system evaluation, you can obtain it from our download page.


    As for the documentation, a short manual is available in the form of an html file. This file also contains a list of currently known bugs - if you encounter some new ones, please tell us and we will include them into the list and try to solve them (sometimes in the future :-)).

    Further information can be found in the articles accessible from the PNtalk Project Home Page. We especially recommend you the article PNtalk - A Computerized Tool for Object Oriented Petri Nets Modelling.


    There are several examples of OOPNs ready for downloading here in the form of common UNIX gzip and DOS pkzip archives:
  • Ackermann - computes the value of the Ackermann function for given parametres.
    Recommended simulation options: step-by-step or automatic normal mode.
  • Adder - reads two numbers, adds them and displays the result.
    Recommended simulation options: step-by-step or automatic normal mode.
  • Hierarchy - demostrates a possibility of using subpages in PNtalk.
    Recommended simulation options: step-by-step normal mode.
  • MedicalCentre - a simulation model of a simple medical centre demonstrating the way of using time and statistics in PNtalk.
    Recommended simulation options: fast automatic weak mode with simulation time (e.g. 0-50000).
  • NormalMode - a demonstration of what changes of the state can be detected by the normal mode.
    Recommended simulation options: step-by-step normal mode with carefully watching changes in transitions' enabling.
  • PatientsAndDoctors - a simple model of a world consisting of doctors and patients. It demonstrates the usage of active objects, inheritance, predicates and methods in PNtalk.
    Recommended simulation options: step-by-step normal mode with simulation time e.g. 0-100.
  • Russian Philosophers
    • RussianPh - this is a model of the problem of five Russian philosophers. They think not about general problems but about the problem of five Russian philosophers they are taking part in. They start getting forks whenever problems in their minds block. To make the problem finite, the last level of Russian philosophers does not think about Russian philosophers but about the classical ones. (This problem was originally provided in a sligthly different way by C.A. Lakos.)
      Recommended simulation options: step-by-step normal mode or automatic fast mode.
    • SimplRussianPh - this is a modification of the classical problem of five philosophers competing for shared forks. In this case, philosophers are thinking about the situation they are in not only when having rest but uninterruptedly. On the other hand, they have to additionaly ask for meal and then return plates. It is impossible so that one philosopher will eat twice whereas another not at all.
      Recommended simulation options: step-by-step normal mode.
    • SimplRussPhGr - this a simple graphical visualisation of the problem of the simplified russian philosophers. Particular philosophers are depicted by circles with colours changing wrt. their states. Nesting depicts the layers of thinking.
      Recommended simulation options: automatic fast mode.
  • Seasons - a trivial net describing changing of the year seasons and intended for giving an example of a net suitable for using the wek mode.
    Recommended simulation options: step-by-step weak mode.
  • StrongMode - a demonstration of what changes of the state can be detected by the strong mode.
    Recommended simulation options: step-by-step strong mode with carefully watching changes in transitions' enabling.
    • [PNtalk Project Home Page]

    If you have any comments to this page or to the PNtalk system please send a message to vojnar@dcse.fee.vutbr.cz.
    Last modified at 8/5/1997.