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Systems Engineering Project: System Validation and Verification Using SDL

This project explores Formalisms for Automated V&V using SDL, MSC, & TTCN. It discusses SDL characteristics, evolution, commercial tools, methodology, and project summary. Challenges and highlights of using Tau/SDL tool are also captured.

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Systems Engineering Project: System Validation and Verification Using SDL

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  1. Systems Engineering Project:System Validation and VerificationUsing SDL Ron Henry ENSE 623 November 30, 2004

  2. Formalisms for Automated V&V • Several standard notations have evolved in support of automated validation and verification: • Specification and Description Language (SDL) • Message Sequence Charts (MSC) • Test and Test Control Notation (TTCN) • These formalisms are considered complementary • MSCs (familiar from UML sequence diagrams) are used both to specify requirements and to trace execution • SDL is used to specify the system architecture and state-machine model • TTCN is an abstract representation for test cases

  3. Characteristics of SDL • Major language features • Formal, hierarchical data flow diagrams • Extended finite state machines (EFSMs) • Local variables • Timers • SDL Evolution • Widely used in telecommunications industry • First ITU Z.100 recommendation in 1980 • Updated every 4 years • SDL-92 added support for object-oriented features • SDL-2000 adds support for hierarchical EFSMs (equivalent to Statecharts)

  4. Commercial Tools for SDL-Based V&V • Tools can provide a variety of functions • Graphical editing & syntax checking • Model checking (static analysis) • Executable simulation & animation of a model • Validation of a model against a use case • Specification-based generation of test cases • Telelogic appears to be market leader in this area • Tau/SDL is one of the leading tools • ObjectGeode also acquired by Telelogic • SAFIRE-SDL by Solinet • Tau/SDL was used for this project • 15 licenses available under arrangement with UMD (handled through Prof. Basili in CS dept.) • C compiler (Borland recommended) must be installed in order to generate executables for simulation and validation

  5. General Methodology

  6. Remote Observing Platform: System Context

  7. Remote Observing Platform: Domain Model

  8. MSC TurnOnInstrument

  9. MSC TurnOffInstrument

  10. MSC Observe

  11. Tau/SDL Model Structure

  12. Observatory System Diagram

  13. InstrumentModule Block Diagram

  14. CAM1 Block Diagram

  15. Shutter Process Diagram

  16. CameraManager Process Diagram

  17. Inheritance in SDL: HomingCameraManager

  18. Tau/SDL Simulator User Interface

  19. MSC Observe: Process-Level Simulator Trace

  20. Tau/SDL Validator User Interface

  21. Tau/SDL Validator Report Summary

  22. Tau/SDL Validator Trace: Implicit Signal Consumption

  23. Model Validation: MSC TurnOnInstrument

  24. Model Validation: MSC Observe

  25. MSC-Based Testing: TTCN Structure

  26. Test Case Generated from Observe MSC

  27. V&V with SDL: Project Summary • This project has demonstrated a robust framework for V&V based on SDL • Hierarchical data flow diagrams are well suited to formalizing complex system architectures • V&V is accomplished through following steps: 1. Basic usability testing and sanity checking is done manually using a simulator 2. SDL model is automatically validated against use cases in the form of MSCs 3. MSCs are then used to generate TTCN test cases • Tau/SDL is a powerful tool, but its complexity presented challenges • Not all features worked • Generated executables subject to unexplained crashes • Error messages not always clear

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