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Learning goals

After following this tutorial, you will be able to:

  • Understand when to use ‘external’ and what problems it solves

  • Understand the impact of using the ‘external’ keyword in your Dezyne models

  • Identify where to implement additional logic in your models to support the usage of ‘external’

  • Use the Dezyne verification & simulation tools to correctly implement a solution using the ‘external’ keyword

Intended audience and prerequisites

As this tutorial will build upon the basic features of Dezyne, it is assumed that you are familiar with the Dezyne syntax and the use of Dezyne verification and simulation tools. It is helpful if you have some knowledge on the Dezyne runtime, which can be found in the previous tutorial.

This tutorial will consist of two parts: first we will disclose some information on how simulation and verification by Dezyne works and what the effects are of using ‘external’. The second part of the tutorial will focus on designing a solution for the problems that can be found with ‘external’.

The nature of ‘external’ requires you to be able to think in terms of threads and sequencing of events across multiple threads. You will be assisted in this during the tutorial, but it helps if you are familiar with the concepts.

This tutorial will build further upon the Alarm System models and native implementation from the previous tutorials. With ‘external’, we will be able to discover interesting real-world behavior in the Alarm System that can lead to illegality in its components.

Platform choice

As most of the work can be done in the Dezyne modeling language and only minimal changes are required on the platform, the platform choice from previous tutorials remains unchanged. Raspbian with g++ 4.9.2 on the Raspberry Pi supports all language requirements for using a thread-safe-shell in C++11.

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