1. 1 Design Methods for Reactive Systems, R.J. Wieringa Part V: Communication Notations

2. 2 Outline zData flow diagrams (DFDs) zCommunication diagrams zContext modelling zRequirements-level architectures

3. 3 Where are we?

4. 4 Data flow diagrams (DFDs): heating controller example A collection of communicating data stores and processes

5. 5 Data flow diagrams (DFDs): hierarchical structuring; tank control process Data process specification: Lower-level DFD

6. 6 Data flow diagrams (DFDs): basic concepts (1) zFlow: Instantaneous and reliable communication channel

7. 7 Data flow diagrams (DFDs): basic concepts (2) zStores: Remembers the data written to it

8. 8 Data flow diagrams (DFDs): basic concepts (2) zProcess: Some system activity yData process yControl process yComposite process zStateless or stateful processes zSyntax:

9. 9 Data flow diagrams (DFDs): control process specification; STD for heater control process Note consistency with DFD

10. 10 Communication diagrams: basics zDFDs instance-level; communication diagrams possibly type-level zUsed to represent requirements-level architectures z”Language”

11. 11 Communication diagrams: heating controller example Nodes ~ components Edges ~ communication channels

12. 12 Communication diagrams: heating controller; instance-level

13. 13 Communication diagrams: components

14. 14 Communication diagrams: decomposition

15. 15 Communication diagrams: decomposition and closely coupled components

16. 16 Communication diagrams: decomposition and closely coupled components; elevator controller

17. 17 Communication diagrams: allocation of functions to components (allocation table)

18. 18 Communication diagrams: flowdown

19. 19 Context modelling: motivation

20. 20 Context modelling: alternative system boundaries for the elevator controller

21. 21 Contex modelling: context boundary

22. 22 Context modelling: context diagram for the training information system We need not only worry about the system boundary, but also about the context boundary … see guidelines

23. 23 Context modelling: structuring the context

24. 24 Context modelling: structure in the context of a information-provision system

25. 25 Context modelling: structure in the context of a directive system

26. 26 Context modelling: structure in the context of manipulative system

27. 27 Requirements-level architectures: architectures in general We now move from modelling what is given to designing the SuD

28. 28 Requirements-level architectures: input sources

29. 29 Requirements-level architectures: encapsulation versus layering

30. 30 Requirements-level architectures: architectural styles zData flow style: yNot applicable to reactive systems zVon Neumann style yStrict separation of data storage and data processing yDatabase and application programs zObject-oriented style yProcessing and storage encapsulated in objects

31. 31 Requirements-level architectures: comparison with implementation-level architectures

32. 32 Requirements-level architectures: main decomposition approaches zFunctional decomposition yeach system function is allocated to a different component zSubject-oriented decomposition yeach group of subject domain entities corresponds to a system component

33. 33 Requirements-level architectures: functional decomposition, object-oriented style; the ticket system example

34. 34 Requirements-level architectures: subject-oriented decomposition, object-oriented style; the ticket system example

35. 35 Requirements-level architectures: mixed architecture

36. 36 Requirements-level architectures: communication-oriented decomposition

37. 37 Requirements-level architectures: evaluation criteria

38. 38 Summary zData flow diagrams (DFDs) zCommunication diagrams zContext modelling zRequirements-level architectures