Software LEIC/LETI. Lecture 21

Transcription

1 Software LEIC/LETI Lecture 21

2 Last Lecture Offline concurrency patterns (continuation) Object-relational behavioral patterns Session state patterns

3 Presentation logic Services Domain logic Remote access Data access Remote Service Database Transaction Manager

4 Remote access Remote Service Presentation logic T R A Services N S Domain logic A C T I O N S Data access Database Transaction Manager

5 Today Requirements Engineering

6 Requirements Engineering no man s land

7 Understand what needs to be solved

8

9 Problem

10 Problem

11 Problem Solution

12 Problem Solution becames

13 becames Problem Solution Problem

14 becames Problem Solution Problem

15 becames Problem Solution Problem Solution

16 The scope

17

18

19 User Requirements

20 User Requirements

21 User Requirements

22 User Requirements

23 User Requirements System Requirements

24 User Requirements System Requirements

25 the solution from the user perspective User Requirements System Requirements

26 the solution from the user perspective the problem from the developers perspective User Requirements System Requirements

27 the solution from the user perspective the problem from the developers perspective User Requirements System Requirements The Problem Space

28 (Fig 4.1, Sommerville)

29 (Fig 4.2, Sommerville)

30 Functional and Non-functional Requirements system behaviour and its constraints

31

32 create an account

33 create an account transactions should execute in less than 1 second

34 create an account transactions should execute in less than 1 second process an adventure

35 create an account transactions should execute in less than 1 second process an adventure system is unavailable 5 minutes per day maximum

36 create an account transactions should execute in less than 1 second process an adventure system is unavailable 5 minutes per day maximum only authorized users can use the system

37 create an account transactions should execute in less than 1 second process an adventure system is unavailable 5 minutes per day maximum only authorized users can use the system

38 Is Login functional or non-functional?

39 (Fig 4.3, Sommerville)

40 (Fig 4.4, Sommerville)

41 (Fig 4.5, Sommerville)

42 Qualities of Requirements

43 complete Qualities of Requirements

44 complete consistent Qualities of Requirements

45 complete consistent measurable Qualities of Requirements

46 Is it easy to achieve the qualities aimed for requirements?

47 Completeness do they capture all relevant aspects

48 Consistent different stakeholders security vs availability

49 Measurable the system should resist attacks

50 Software Requirements Document

51 (Fig 4.16, Sommerville)

52 (Fig 4.17, Sommerville)

53 How to describe requirements?

54 (Fig 4.11, Sommerville)

55 what about test cases? (Fig 4.11, Sommerville)

56 natural language (Fig 4.12, Sommerville)

57 structured natural language (Fig 4.13, Sommerville)

58 tabular specification (Fig 4.14, Sommerville)

59 graphical notation (Fig 4.15, Sommerville)

60 formal specification

61 formal specification what is the difference from a tabular specification?

62 formal specification what is the difference from a tabular specification? wait for Dafny and see ;)

63 Requirements Engineering Process

64 (Fig 4.6, Sommerville)

65 Requirements Elicitation and Analysis

66 (Fig 4.7, Sommerville)

67 (Fig 4.7, Sommerville) interviewing

68 interviewing ethnography (Fig 4.7, Sommerville)

69 interviewing ethnography stories (Fig 4.7, Sommerville)

70 interviewing ethnography stories scenarios (Fig 4.7, Sommerville)

71 (Fig 4.9, Sommerville)

72 (Fig 4.10, Sommerville)

73 Requirements Validation

74 (Fig 4.18, Sommerville)

75 TYPES (Fig 4.18, Sommerville)

76 TYPES validity checks (real needs) (Fig 4.18, Sommerville)

77 TYPES validity checks (real needs) consistency checks (Fig 4.18, Sommerville)

78 TYPES validity checks (real needs) consistency checks completeness checks (Fig 4.18, Sommerville)

79 TYPES validity checks (real needs) consistency checks completeness checks realism checks (Fig 4.18, Sommerville)

80 TYPES validity checks (real needs) consistency checks completeness checks realism checks verifiability (measure) (Fig 4.18, Sommerville)

81 TYPES validity checks (real needs) consistency checks completeness checks realism checks verifiability (measure) VALIDATION (Fig 4.18, Sommerville)

82 TYPES validity checks (real needs) consistency checks completeness checks realism checks verifiability (measure) VALIDATION (Fig 4.18, Sommerville) reviews

83 TYPES validity checks (real needs) consistency checks completeness checks realism checks verifiability (measure) VALIDATION (Fig 4.18, Sommerville) reviews prototyping

84 TYPES validity checks (real needs) consistency checks completeness checks realism checks verifiability (measure) VALIDATION (Fig 4.18, Sommerville) reviews prototyping test-case generation

85 Requirements Management

86 Planning

87 Planning large number of requirements

88 Planning large number of requirements

89 Planning identification large number of requirements

90 Planning identification large number change management of requirements

91 Planning identification large number of requirements change management traceability

92 Planning identification large number of requirements change management traceability tool support

93 (Fig 4.19, Sommerville) Requirements Change Management

94 Agile Requirements

95 stories Agile Requirements

96 value stories and dimension Agile Requirements

97 value stories and dimension Agile Requirements product backlog

98 value stories and dimension Agile Requirements product backlog can be changed

99 value stories and dimension Agile Requirements product backlog can be changed sprint backlog

100 value stories and dimension Agile Requirements product backlog can be changed sprint backlog preserve goal

101 Complete specifications are not always possible S, P, and E systems?

102 Lehman s Law

103 Different classifications of software systems

104 In S-systems the problem is formally defined math library

105 Implement the specification

106 P-systems implement a model of the problem chess game

107 Define the abstraction and implement it

108 E-systems implements a model of the problem, which becomes part of the reality automated stock trading

109 Define the abstraction, implement it, and change the world

110 The impact of Lehman s Law on Requirements Engineering? the requirements are a model of reality and models change