Browsing by Author "Dewar, Alan"

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    A distributed software prototyping and simulation environment: JADE
    (1985-10-01) Unger, Brian W; Dewar, Alan; Cleary, John; Birtwistle, Graham
    Jade is an environment that supports the development of distributed software. Components may be written in any of a number of different languages. A common inter-process communication protocol provides a uniform interface among the components. A window system allows the user to interact with many different processes at once. A hierarchical graphics system is provided for use with documentation and programming, and for support of monitoring. Monitoring in Jade is also supported by an extensible mechanism which allows for multiple views of the same process. The non- determinism of distributed systems may be controlled in order to provide repeatability of executions and to aid in testing and debugging. Finally, the formal specification of inter-process events in Jade is supported by a communications protocol verifier, allowing run-time consistency checking. Together, these tools provide a powerful environment for software prototyping and simulation.
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    Graphical tracing and debugging of simulations
    (1983-11-01) Dewar, Alan; Unger, Brian W
    A graphical approach to the tracing and debugging of simulations is presented. First, a number of desirable features for such a system are briefly outlined. An extension to the Simula class SIMULATION is then described which provides these features for the application programmer. The extension has been designed so that it is simple to use in its default state but is also highly extensible, allowing the programmer to obtain graphical traces quickly or to produce graphical traces of arbitrary complexity. Examples are given illustrating both of these facets and comparing these to a non-graphical trace of the same program. Limitations to the approach are discussed.
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    INTERPRETERS IN LOGIC PROGRAMMING: A POWERFUL TOOL FOR SIMULATION
    (1983-11-01) Cleary, John; Dewar, Alan
    The logic programming language Prolog and extensions to permit asynchronous execution are introduced. Some simple producer/consumer problems are used to illustrate the handling of processes and their synchronization. Some tools that can be used to aid tracing and verifying such programs are described. These include a system that will check whether one version of a program is a refinement of another, and another that allows simple and flexible programming of graphical displays of data structures and executing programs. These are used as examples to support the assertion that logic programming provides very powerful tools for verifying the correctness of simulations and programs.
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    The JADE approach to distributed software development
    (1985-11-01) Unger, Brian W; Dewar, Alan; Cleary, John; Birtwistle, Graham
    Jade is an environment that supports the development of distributed software. Components may be written in any of a number of different languages. A common inter-process communication protocol provides a uniform interface among the components. A window system allows the user to interact with many different processes at once and allows for multiple views of the same process. A hierarchical graphics system is provided for use with documentation and programming, and for support of monitoring. The non-determination of distributed systems may be controlled in order to provide repeatability of executions and to aid in prototyping real-time distributed software. Finally, the formal specification of inter-process events in Jade is supported by a communications protocol verifier, allowing run-time consistency checking. We describe these tools and their use in the development of distributed software for the control of a simulated system of parking lots.