1. UHD-CMS-CH101 Specification Phase Chapter Ten

2. UHD-CMS-CH102 SPECIFICATION DOCUMENT The specification document must be Informal enough for client Formal enough for developers Free of omissions, contradictions, ambiguities

3. UHD-CMS-CH103 SPECIFICATION DOCUMENT Constraints –Cost –Time –Portability –Reliability –Response time Acceptance Criteria –Vital to spell out series of tests –Product passes tests, deemed to satisfy specs. –Some are restatements of constraints

4. UHD-CMS-CH104 SOLUTION STRATEGY General approach to building the product Find strategies without worrying about constraints Modify/select strategies in light of constraints Keep written record of all discarded strategies and why discarded: –To protect spec team –To prevent unwise new solutions during maintenance phase

5. UHD-CMS-CH105 SPECIFICATION METHODS Informal Semi-formal formal

6. UHD-CMS-CH106 INFORMAL SPECIFICATIONS Example: “if sales of current month are below target sales, then report is to be printed, unless difference between target sales and actual sales is less than half of difference between target sales and actual sales in previous month, or if difference between target sales and actual sales for the current month is under 5%”

7. UHD-CMS-CH107 INFORMAL SPECIFICATIONS Based on Natural Languages Can be ambiguous Claim: –ambiguity can not arise when specs done by professionals Refutation: –Text Processing case (see textbook)

8. UHD-CMS-CH108 INFORMAL SPECIFICATIONS Conclusion: Natural Language NOT good way to specify product Fact: –Many organizations still use natural language, especially for commercial products Reasons: –Uninformed management –Under-trained computer professionals –Management gives in to client pressure –Management unwilling to invest in training

9. UHD-CMS-CH109 STRUCTURED SYSTEMS ANALYSIS Three popular graphical specification methods –DeMarco –Gane and Sarsen –Yourdon Equivalent Equally good Many US corporations use them for commercial products Gane and Sarsen used for Object-Oriented design

10. UHD-CMS-CH1010 SSA: CASE STUDY Sally’s Software Store buys software from various suppliers and sells it to the public. Popular software packages are kept in stock, but the rest must be ordered as required. Institution and corporations are given credit facilities, as are some individuals. Sally’s store is doing well, but despite her business success Sally has been advised to computerize. Should she? Better question: what part?

11. UHD-CMS-CH1011 CASE STUDY Fundamental issue –What is Sally’s objective in computerizing her business? Assume –Objective is “to make more money” Cost/benefit analysis for each section of business.

12. UHD-CMS-CH1012 CASE STUDY Gane and Sarsen Technique: A nine step method Stepwise refinement in many steps

13. UHD-CMS-CH1013 CASE STUDY Data flow diagram (DFD) shows logical data flow (what happens, not how it happens)

14. UHD-CMS-CH1014 STEP 1: DRAW THE DFD First refinement

15. UHD-CMS-CH1015 STEP 1- Second Refinement

16. UHD-CMS-CH1016 STEP 1- Portion of third refinement

17. UHD-CMS-CH1017 STEP 1 contd Final DFD –Larger, BUT easily understood by client Larger DFDs –Hierarchy of DFDs –Each box becomes DFD at a lower level

18. UHD-CMS-CH1018 STEP 2: Decide what parts to computerize cost/benefit analysis STEP 3: Refine data flow Data items for each data flow Refine each flow stepwise order: order identifications customer details package details Refine further Need data dictionary

19. UHD-CMS-CH1019 STEP4: Refine Logic of Processes Example: Process: Give educational discount –Sally must explain discount for educational institutions –10% on up to 4 packages, 15% on 5 or more Translate into decision tree

20. UHD-CMS-CH1020 STEP 5: Refine Data Stores Define contents and representation (format) Specify where immediate access is required –define type of queries –define Data Immediate Access Diagram (DIAD)

21. UHD-CMS-CH1021 STEP 6: Define Physical Resources For each file, specify –File name –Organization –Storage medium –Records (to field level) DBMS: –define each table STEP 7: Determine I/O Specs Specify input forms, input screens, printed output

22. UHD-CMS-CH1022 STEP 8: Perform Sizing Determine data for step 9: –Volume of input (daily or hourly) –Size, frequency. Deadline for each printer report –Size, number of records processed –Size of each file

23. UHD-CMS-CH1023 STEP 9: Hardware Requirements –Mass Storage requirements –Input needs –Output devices –Is existing hardware adequate? However –Response time can NOT be determined

24. UHD-CMS-CH1024 ENTITY-RELATIONSHIP DIAGRAMS Semi-Formal technique Data-Oriented Widely used in specifying databases used for Object-Oriented Analysis Example: Author, Biography, Reader

25. UHD-CMS-CH1025 ENTITY-RELATIONSHIP DIAGRAMS 1-to-many relationships

26. UHD-CMS-CH1026 ENTITY-RELATIONSHIP DIAGRAMS Many-to-many relationships

27. UHD-CMS-CH1027 FORMAL TECHNIQUES Finite State Machines Petri Nets Z

28. UHD-CMS-CH1028 FINITE STATE MACHINES A safe has a combination lock that can be in one of three positions labeled 1, 2 and 3. The dial can be turned left or right (L or R). Thus there are 6 possible dial movements: 1L, 1R, 2L, 2R, 3L, and 3R. The combination to the safe is 1L, 3R, 2L. Any other dial movement cause the alarm to go off.

29. UHD-CMS-CH1029 FINITE STATE MACHINES Set of states: (SafeLocked, A, B, SafeUnlocked, SoundAlarm) Set of inputs:( 1L, 1R, 2L, 2R, 3L, 3R) Transition function: Initial State: SafeLocked Set if final states: (SafeUnlocked, SoundAlarm)

30. UHD-CMS-CH1030 FSM--State Transition Diagram(STD)

31. UHD-CMS-CH1031 FSM--State Transition Table

32. UHD-CMS-CH1032 EXTENDED FSM Extended FSM with global predicates –predicate: condition in terms of global state/event or a combination of them Transition rules have form: –State and Event and Predicate ==> New State

33. UHD-CMS-CH1033 ELEVATOR PROBLEM

34. UHD-CMS-CH1034 ELEVATOR PROBLEM

35. UHD-CMS-CH1035 ELEVATOR PROBLEM

36. UHD-CMS-CH1036 ELEVATOR PROBLEM

37. UHD-CMS-CH1037 ELEVATOR PROBLEM

38. UHD-CMS-CH1038 ELEVATOR PROBLEM

39. UHD-CMS-CH1039 ELEVATOR PROBLEM

40. UHD-CMS-CH1040

41. UHD-CMS-CH1041 POWER OF FSM TO SPEC COMPLEX SYSTEMS Specs take simple form Specification is –Easy to write down –Easy to validate –Easy to convert into design –Easy to generate code automatically –More precise than graphical methods –Almost as easy to understand However –Timing considerations not handled

42. UHD-CMS-CH1042 WHO IS USING FSMS? Commercial Products –Menu driven –Various states/screens –Automatic code generation a major plus System Software –Operating systems –Word processors –Spreadsheets CASE tools –Statemate

43. UHD-CMS-CH1043 PETRI NETS Powerful technique for specifying systems with potential timing problems –Concurrency and synchronization –Race conditions –Deadlock –originally used by automata theorists –now used in performance evaluation, O/S, and SE fields

44. UHD-CMS-CH1044 Formal Specifications - Cont. Z –a formal specification language –uses set theory, functions, and discrete math. –Initially difficult to learn –the most widely language

45. UHD-CMS-CH1045 Testing during Spec. Phase Walkthrough Inspection (more powerful) –team of inspectors checks specs against a checklist If a formal tech. is used other testing tech. such as correctness-proving methods can be applied, simulation of FSM/Petri Nets etc.

46. UHD-CMS-CH1046 CASE tools Two classes –Graphical tools DFD, FSMs, Petri nets, ER diagrams –Data dictionary the two should be integrated E.g., –Analyst/Designer, Excelerator, software through pictures, system architect, and Teamwork

47. UHD-CMS-CH1047 Metrics Five fundamental metrics –size number of items in the data dictionary –cost –duration – effort –quality number faults found during inspection This information is tentative at best