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

2. 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. 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. 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. 5 General Methodology

6. 6 Remote Observing Platform: System Context

7. 7 Remote Observing Platform: Domain Model

8. 8 MSC TurnOnInstrument

9. 9 MSC TurnOffInstrument

10. 10 MSC Observe

11. 11 Tau/SDL Model Structure

12. 12 Observatory System Diagram

13. 13 InstrumentModule Block Diagram

14. 14 CAM1 Block Diagram

15. 15 Shutter Process Diagram

16. 16 CameraManager Process Diagram

17. 17 Inheritance in SDL: HomingCameraManager

18. 18 Tau/SDL Simulator User Interface

19. 19 MSC Observe: Process-Level Simulator Trace

20. 20 Tau/SDL Validator User Interface

21. 21 Tau/SDL Validator Report Summary

22. 22 Tau/SDL Validator Trace: Implicit Signal Consumption

23. 23 Model Validation: MSC TurnOnInstrument

24. 24 Model Validation: MSC Observe

25. 25 MSC-Based Testing: TTCN Structure

26. 26 Test Case Generated from Observe MSC

27. 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