1. Requirements Management with Use Cases Module 7: Refine the System Definition Requirements Management with Use Cases Module 7: Refine the System Definition

2. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 2 Where Are We in The Requirements Workflow?

3. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 3 Refine the System Definition: Module Objectives  Decide on the detailed software requirements  Define the Software Requirements Specification  Detail the use cases  Detail the declarative requirements  Learn qualities of good requirements

4. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 4 Refine the System Definition: Activities and Artifacts

5. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 5 Refine the System: Software Requirements Focus Problem Solution Space Problem Space Needs Features Software Requirements Test Procedures DesignUser Docs The Product To Be Built Traceability

6. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 6 What Do Software Requirements Specify? System Inputs Outputs Functions Performance Environments

7. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 7 Features Drive Software Requirements Feat 63 - the defect tracking system will provide trending information to help the project manager assess project status Trending information will be charted with a line graph showing time on the x axis, and number of defects found on the y axis. Trending periods can be entered in units of days, weeks or months. An example trend report is shown in Figure 1: Print Status Report Operator Project Manager

8. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 8 Specifying the Software Requirements Features Software Requirements Needs The Software Requirements Specification (SRS) package defines complete external behavior and characteristics of the system to be built Vision Document Supplementary Specifications Use-Case Model SRS SRS Package

9. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 9 Roles of the SRS Package  Basis of communication between all parties  Contractual agreement between parties  Basis for development: design, implement, test Supplementary Specifications Use-Case Model SRS SRS Package

10. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 10 Who Uses the SRS Package?  Client team  Customer: approve what system should do  Users: understand what system should do  Developer team  Use-case and requirements specifiers: refine software requirements  Designers: find design classes  Testers: use as basis for test cases  Project Manager: manage the project  Technical Writers: write user’s guide Remember the SRS is for people to read, not for computers

11. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 11 1. Introduction 1.1 Purpose 1.2 Scope 1.3 Definitions, Acronyms, and Abbreviations 1.4 References 1.5 Overview 2. Overall Description 2.1 Use-Case Model Survey 2.2 Assumptions and Dependencies 3. Specific Requirements 3.1 Use Case Reports 3.1.1 3.1.2... 3.2 Supplementary Specifications 3.2.1 Usability Requirements 3.2.2 … 4. Supporting Information Appendices Index 1. Introduction 1.1 Purpose 1.2 Scope 1.3 Definitions, Acronyms, and Abbreviations 1.4 References 1.5 Overview 2. Overall Description 2.1 Use-Case Model Survey 2.2 Assumptions and Dependencies 3. Specific Requirements 3.1 Use Case Reports 3.1.1 3.1.2... 3.2 Supplementary Specifications 3.2.1 Usability Requirements 3.2.2 … 4. Supporting Information Appendices Index What Is In An SRS Package? TP7:SRS Package Template

12. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 12 Documents Project Repository Where to Store The Items in The SRS Package? The mechanics of where to store depend on  Available tools  Developer environment and preferences  Client environment and preferences

13. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 13 How to Specify Functional Requirements ? Use Cases Declarative Statements The system shall … The system shall... ? Which one to choose?

14. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 14 How to Specify Functional Requirements ?  Recommendation  Use Both Use Cases and Declarative Statements Both are necessary to understand any system of significant complexity  Preference for uses cases, where appropriate Use Cases Declarative Statements The system shall … The system shall... +

15. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 15 SRS Variations For Functional Requirements Use Cases Declarative StatementsUse Cases Declarative Statements Situation 1Situation 2 The system …

16. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 16 Specifying Software Requirements in Use Cases  Each use case  Describes actions the system takes to deliver something of value to the actor  Shows the system functionality that an actor uses  Models a dialogue between the system and actors  Is a complete and meaningful flow of events, from the perspective of a particular actor Use-Case Model

17. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 17 * 1. Brief Description* 2. Flow of Events* Basic Flow of Events Alternative Flows of Events 3. Special Requirements 4. Pre-Conditions 5. Post-Conditions 6. Extension Points 7. Relationships* 8. Use-Case Diagrams 9. Other Diagrams/enclosures * 1. Brief Description* 2. Flow of Events* Basic Flow of Events Alternative Flows of Events 3. Special Requirements 4. Pre-Conditions 5. Post-Conditions 6. Extension Points 7. Relationships* 8. Use-Case Diagrams 9. Other Diagrams/enclosures Use-Case Report: Template The Use-Case Report contains detailed information about an individual use case TP5: Use Case Report Template

18. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 18 Use-Case Properties in the Use-Case Report  Name (same as in Use-Case-Model Survey)  Brief description (same as in Use-Case-Model Survey)  Flow of events  The use case’s behavior  What the actors do, what the system does in response  Special requirements  Requirements about this use case not covered in flow of events  Usually non-functional requirements  Pre-conditions  Constraints on when the use case may start  Post-conditions  Constraints on the system after the use case has ended

19. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 19 Use-Case Properties in the Use-Case Report (cont.)  Extension points  Places in the flow of events to attach extensions  Relationships (same as in Use-Case-Model Survey)  Associations with actors and with other use cases  Use-Case diagrams  Visual model of all relationships involving this use case  Other Diagrams or enclosures  Interaction, activity, or other diagrams  Pictures of the user interface

20. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 20 Sample Basic Flow of Events Withdraw Cash Use Case 1. Insert Bank Card This use case begins when the Bank Customer inserts a bank card in the card reader on the ATM machine. The ATM validates the card. 2. Enter PIN The ATM asks for the customer PIN code. The Bank Customer enters the PIN code. 3 Select ‘Withdraw Cash’ The ATM displays the different alternatives that are available on this unit. The Bank Customer selects “Withdraw Cash”.

21. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 21 Sample Basic Flow of Events (cont.) 4. Enter Account and Amount The ATM asks for account to withdraw from and amount to withdraw. The Bank Customer enters account and amount. 5. Debit Bank Account The ATM sends the card id, PIN, amount and account to the Bank Consortium. The Bank Consortium replies that the transaction is accepted. The ATM system reports to the Bank Customer that it is ready to dispense cash. 6. Print Receipt The ATM asks the Bank Customer if a receipt is desired. The Bank Customer requests a receipt. The ATM system prints the receipt. 7. Receive Cash and Card The ATM system dispenses money to the Bank Customer, and returns the Bank Card. The use case ends.

22. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 22 Sample Alternative Flows of Events A1. Bank Card Not Valid If in Step 1, Insert Bank Card, the card is not valid, it is ejected to the Bank Customer with a "sorry not a valid card" message. The use case ends. A2. Wrong PIN If in Step 5, Debit Bank Account, the Bank Consortium reply indicates a wrong PIN. The message "wrong PIN" is shown to the Bank Customer. The Bank Customer has three tries to get it right. If the Bank Customer correctly enters the PIN, the basic flow resumes at Step 4, Enter Account and Amount. Otherwise the card is kept by the ATM machine and the use case ends. What other alternatives can you think of?

23. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 23 Exercise: Choosing a Style for the Flow of Events  Read the different flow of events descriptions on the following three (3) slides and answer the following questions:  Who is the intended audience?  Which is the easiest to understand (read)?  Which do you think is the easiest to write?  Is any one “better” than the others?  Which one do you prefer? Why?

24. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 24 Flow of Events - Style Type I Orderers can create Orders to collect measurement data from Network Elements. The system will assign the Order a unique name and default values for when and how long the measurement should be and also how often it is to be repeated. These values can of course be edited by the Orderer. The Orderer must further specify which measurement function, network element and measurement objects to apply. The Orderer can also add a personal comment to the order. When necessary information is defined, a new Order is created and initialized with the defined attributes, the name of the creator, date of creation, and status of the order will be set to 'scheduled'. (Possible values for the status are: Scheduled, Executing, Completed, Canceled, and Erroneous). The Operator is then notified that a new Order has been created and receives a reference to the new Order so that it can be displayed.

25. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 25 1. Request a Measurement Order This use case starts when the Operator requests a Measurement Order. The system displays all available Network Elements that the operator has the authority to access. 2. Configure Network Elements The operator selects which network elements to measure, and chooses measurement objects and functions for each selected network element. The operator indicates he is finished configuring network elements. 3. Specify Measurements The system give the measurement order a unique name and displays default values for when, how often, and for how long the measurements should be made. The operator edits the default values as needed. The operator optionally enters a comment on the order. 4. Create Measurement Order The operator requests the system to create the measurement order. The system confirms creation of the measurement order with the operator and provides a reference to it. The use case ends. Flow of Events - Style Type II

26. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 26 Flow of Events - Style Type III => 'Administrator order' (User identity) REPEAT <='Show administrator order menu' IF (=> 'Creating an Order' (Measurement function, network element, measurement object)) THEN The system finds a unique name, default values for when, how often and for how long the measurement should be executed. <= 'Show order' (Default attributes) REPEAT => 'Edit order' (Attribute to change, New value of attribute) <= 'Update screen' (New attributes) UNTIL (All attributes are defined) REPEAT IF (=> 'Edit order' (Attribute to change, New value of attribute)) THEN <= 'Update screen' (New attributes) ELSIF (=> 'Save order' (Order identity, Attributes)) THEN The order is created and initialized in the system with the defined attributes, the name of the creator, date of creation and the status 'scheduled'.) ENDIF UNTIL (=> 'Quit') ENDIF UNTIL 'Quit administrator order'

27. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 27 Exercise: Perspectives in Flow of Events  Now, read the different flow of events descriptions on the following two (2) slides and answer the following questions:  Who is the intended audience?  Which is the easiest to understand (read)?  Which do you think is the easiest to write?  Is one “better” than the other?  Which one do you prefer? Why?

28. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 28 Outside Perspective Flow of Events 1. The use case starts when the subscriber lifts the phone, and gets a dial tone. 2. The dial tone disappears when the subscriber dials the first digit. 3. The subscriber dials the rest of the number and will then hear a ring tone if the called party is not busy. 4. The ring tone will disappear if the called party answers the phone call. 5. The call continues until both parties hang up their phones. 6. If the called party is busy the subscriber will hear a busy tone and will then hang up the phone. Local Call Subscriber

29. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 29 Inside Perspective Flow of Events 1. The use case is initiated when the subscriber lifts the phone and the system finds the correct subscriber object, marks it busy and gives a dial tone to the subscriber. 2.The system turns off the dial tone when the subscriber dials the first digit. The system loads the digit into a register and will then wait to receive and store the rest of the digits. 3.When the system has received enough digits it will start to analyze the received digits. 4.When the whole number has been analyzed the system will find the corresponding subscriber object and check whether or not it is marked busy. 5.If the called party is not busy the system will busy mark the object and start... Local Call Subscriber

30. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 30 How to Refine a Use Case Flow of Events  Gradually add detail to the step-by-step outline  Work together with users to refine the outline Include all events in the outline Sketch outlines on large paper Expect to revise the outline many times  First refine the Basic Flow of Events What normally happens  Then refine the Alternative Flows

31. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 31 Questions To Help Detail The Flow of Events  Sequence  What event starts the use case?  How does the use case end?  How does the use case repeat some behavior?  Are there optional situations in the use case?  Action  What does each actor do?  What does the system do?  Interaction  How does the use case interact with actors?  What data is exchanged with actors?

32. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 32 What does NOT belong in the Flow of Events?  Do NOT describe  Events outside the use case In other use cases Between an actor and others outside the system  System operations not visible externally  Details of the user interface Unless it is an important requirement  Avoid vague terminology  Such as “for example”, “etc. ” and “information”

33. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 33 Guidelines For Refining the Basic Flow of Events  Structure the basic flow into steps  Give each step a number and/or a title  Describe each step in 1-3 sentences  Make each step a roundtrip of events  What the Actor does: When the requests to...  What the System does in response: sends message to and...

34. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 34 Exercise: Detail the Basic Flow of Events  Describe each step in the basic flow of events for one or more use cases in your project  Start with the step-by-step outlines written for your use case model (in Unit 5)  Give each step a title  Describe each step in more detail: add 1 to 3 sentences  Focus only on the normal “happy day” path through the use case. No alternative flows, yet!  Write neatly so that you can copy and distribute the text to the rest of the group

35. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 35 Why Divide a Flow of Events into Alternative Flows?  Keep basic flow short and easy to read  Isolate optional sequences Variant events Optional events Exceptions and errors  Isolate sequences executed several times in same flow  Clarify traceability

36. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 36 How to Refine The Alternative Flows  Use one section for each alternative flow  Give each alternative flow a number and title  Divide into steps only if it helps clarify  Describe what happens in the alternative flow  Where in the basic flow or another subflow the alternative flow starts  The condition for doing the alternative flow  Behavior within the alternative flow  Where basic flow or another subflow is resumed  Describe the order of the alternative flows  Only describe order of flows as fixed, if it is  In other cases, point out that the order is unfixed

37. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 37 Specific Alternative Flows  Occur at a specific step in another flow  Example A3. Not Enough Money in Account If the Bank Consortium finds that there is not enough money in the Bank Customer’s bank account, the ATM sends the Bank Customer an error message "Sorry not enough money”. The Bank Customer has an opportunity to enter a new account and amount.

38. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 38 Specific Alternative Flows  Should make clear references  Where you pick up the sequence of actions  Where you hand it over to another flow  Previous example, with clearer references A3. Not Enough Money in Account In Step 5, Debit the Account, of the basic flow, if the Bank Consortium replies to the ATM that there is not enough money in the Bank Customer’s bank account, the ATM sends the Bank Customer an error message "Sorry not enough money”. The ATM continues at Step 4, Enter Account and Amount, of the basic flow.

39. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 39 General Alternative Flows  Occur anywhere in another flow  Example A4: Quit The ATM will allow the Bank Customer to quit at any time during the use case. The ATM will stop the transaction, log the transaction, and eject the Bank Card. The use case ends.

40. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 40 Another Example: Alternative Flows of Events Basic Flow of Events 1. Request a Measurement Order This use case starts when the Operator requests a Measurement Order. … 2. Configure Network Elements The operator selects which network elements to measure, and chooses... 3. Specify Measurements The system give the measurement order a unique name and displays … 3. Create Order The operator requests the system to create the measurement order.... Alternative Flows of Events A1. No Network Elements Available If, in Step 1, no Network Elements are available to measure for this Operator, the system will inform the operator. The use case then ends. A2. No Measurement Functions Available If, in Step 2, no measurement functions are available for the selected network elements, the Operator may select other Network elements. A3. Cancel Measurement Order The system will allow the Operator to cancel all actions at any point during the use case. The system will delete the Order and then end the use case.

41. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 41 Exercise: Detail the Alternative Flows  Further detail at least three (3) alternative flows for each use case in the previous exercise  Continue the description of the flow of events of the use cases in your class project  Use the alternatives identified in the step-by-step outlines written for your use cases (in Module 5)  Describe clearly what will happen in each alternative  Write neatly so that you can copy and distribute the text to the rest of the group

42. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 42  Using pre- and post-conditions  Pre- and post-conditions are observable to the user  Use only if needed for clarification  A pre-condition  Constraint on when use case can start  NOT the event that starts the use case  A post-condition  Guaranteed true when use case ends  Should apply regardless of alternative flows  May contain different variants Pre- and Post-Conditions

43. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 43 Example of a Pre-Condition Withdraw Cash Pre-condition  The customer has a personally-issued card that fits in the card reader, has been issued a PIN number, and is registered with the banking system. Use only if needed for clarification!

44. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 44 Example of a Post-Condition Withdraw Cash Post-condition  At the end of the use case, all account and transaction logs are balanced, communication with the banking system is reinitialized, and the customer has been returned his card or informed of where it will be sent. Use only if needed for clarification!

45. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 45 What About Requirements NOT in Use Cases?  Use a declarative statement to describe the software requirement  Number and title each requirement  Group related requirements for understandability  Use language users can easily understand  Use simple sentence structure: subject + active verb  Consider using a keyword, for example “shall”  Keep it short: state a requirement in 1 to 3 sentences  Use terms from the glossary

46. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 46 Where Are Declarative Requirements Specified?  Does requirement apply to a particular use case?  Specify in the use case report  In “Special Requirements” property  Does requirement apply to the whole system?  Specify in the “Supplementary Specifications” TP6: Supplementary Specifications Template

47. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 47 Functional Requirements in Declarative Statements  Some functionality is easier to state declaratively  Example: ATM System 1. Internationalization The ATM system shall display all messages and menus in the user’s preferred language.

48. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 48 What about Non-Functional Requirements?  The “URPS” of FURPS  Usability  Reliability  Performance  Supportability  Compliance with Legal and Regulatory requirements  FCC  FDA  DOD  ISO  Design Constraints  Operating systems  Environments  Compatibility  Application standards What are some others?

49. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 49 A Closer Look at the “URPS” of FURPS Grady, 1992 Functionality Feature Set Capabilities Generality Security Usability Human Factors Aesthetics Consistency Documentation Reliability Frequency/Severity of Failure Recoverability Predictability Accuracy MTBF Performance Speed Efficiency Resource Usage Throughput Response Time Supportability Testability Extensibility Adaptability Maintainability Compatibility Configurability Serviceability Installability Localizability Robustness

50. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 50 Examples: Non-Functional Requirements  The ATM System  The system can only handle one customer at a time.  The system has to be available 24 hours a day, 7 days a week, with less than.01% downtime. What are some others? Where should each of these be specified?

51. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 51 Specifying Usability Requirements  Definition of “usability”  The ease with which software can be learned and operated by the intended users  Usability requirements  Training time requirements, measurable task times  User abilities (unsophisticated/sophisticated)  Comparison to other systems that users know and like  On-line help systems, tool tips, documentation needs  Conformity with standards Examples: Windows, style guides, GUI Standards

52. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 52 Davis Workshop, 1993 Specifying Reliability Requirements  Definition of “reliability”  The ability for the software to behave consistently in a user-acceptable manner  Reliability requirements  Availability (xx.xx%)  Accuracy  Mean time between failures (xx hrs)  Max. bugs per/KLOC (0-x)  Bugs by class - critical, significant, minor  Reliability predictors  Lines of code  Complexity metrics

53. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 53 Davis Workshop, 1993 Specifying Performance Requirements  Definition of “performance”  A measure of speed or efficiency of the running system  Performance requirements  Capacity  Throughput  Response time  Memory  Degradation modes  Efficient use of scarce resources Processor, memory, disk, network bandwidth

54. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 54 Davis Workshop, 1993 Specifying Supportability Requirements  Definition of “supportability”  The ability of the software to be easily modified to accommodate enhancements and repairs  Supportability requirements  Languages, DBMS, tools, etc.  Programming standards  Error handling and reporting standards  If not observable, state as intent or goals  If not measurable or observable, it is not a requirement

55. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 55 How to Describe User Interfaces  Enclose sketches of proposed screen appearance with the use-case descriptions  Be careful not to specify too much of the design in the use-case documents

56. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 56 How to Describe Communication Protocols  Specify a communication protocol if the actor is another system or external hardware  The description of the use case should state if some existing protocol is to be used  If the protocol is new, it will be fully described during object-model development

57. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 57 What About Design Constraints?  A requirement allows more than 1 design option  A design is a choice among options  A requirement that leaves no options is a design constraint  Distinguish it from other requirements  Place in a special section of your software requirements  Identify the source of each  Document the rationale for each  Examples  An algorithm that is required to be used  A database system that is required to be used

58. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 58 What How What How What How Stakeholder Needs Product or System Features Software Requirements Specification (Use Cases) Design Spec Test Procedures Documentation Plans “One man’s ceiling is another man’s floor” Davis, 1993 The What vs. How Dilemma Question: How can you tell a requirement from design? Answer: It depends on your point of view.

59. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 59 Exercise: Non-Functional Requirements  For your class project, list at least 5 non-functional requirements  Decide where each non-functional requirement should be specified 1. In the properties of a particular use case Special Requirements Basic flow Alternative flows 2. In the Supplementary Specifications

60. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 60 ref - IEEE 1993 Qualities of a Software Requirement Specification  Correct  Complete  Consistent  Unambiguous  Ranked for importance and stability  Verifiable  Modifiable  Traceable  Understandable

61. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 61 Qualities of an SRS: Correct  A Requirements Specification is “correct” if:  Every requirement within it is something required of the system to be built  For example, every requirement in the SRS contributes to the satisfaction of some need Hint: Involve the people who have the problem or mission ref - Davis ‘93

62. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 62 IEEE 1993 Qualities of an SRS: Complete  A Requirement Specification is “complete” if it contains:  All significant requirements  Responses of the software to all inputs  Full labels and references to figures, tables, diagrams  Definitions of all terms and units of measure (Glossary / Data Dictionary)

63. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 63  A Requirements Specification is “consistent” if:  Individual requirements described in it do not conflict  Hint: Trace all related requirements IEEE 1993 SR101: The power LED shall be illuminated whenever the machine is on. SR841: When the on-button is pressed, no observable results shall occur. Qualities of an SRS: Consistent SR245: When the on-button is pressed, the system shall illuminate the power LED. (Inconsistent)(Consistent)

64. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 64 ref - IEEE 1993 “A shall do B to C” Req. 1 Qualities of an SRS: Unambiguous  A Requirements Specification is “unambiguous” if:  Every requirement within it has only one interpretation

65. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 65 Exercise: Exploring Ambiguity Mary had a little lamb. In the space below, write (or draw) two interpretations of what this sentence means. ref - Gause & Weinberg, 1989

66. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 66 Exploring Ambiguity: Dictionary Definitions had -past of have have -1a: to hold in possession as property 4a: to acquire or get possession of: OBTAIN (best to be had) c: ACCEPT; to have in marriage 5a: to be marked or characterized by (have red hair) 10a: to hold in a position of disadvantage or certain defeat b: TRICK, FOOL (been had by a partner) 12: BEGET, BEAR (have a baby) 13: to partake of (have dinner) 14: BRIBE, SUBORN (can be had for a price) lamb - 1a: a young sheep esp. less than one year old or without permanent teeth b: the young of various other animals (as smaller antelopes) 2a: a person as gentle or weak as a lamb b: DEAR, PET c: a person easily cheated or deceived especially in trading securities 3a: the flesh of lamb used as food

67. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 67 Exploring Ambiguity: Analysis havelambInterpretation 1a1aMary owned a little sheep under one year of age or without permanent teeth. 4a1aMary acquired a little sheep under one year of age or without permanent teeth. 5a1aMary is the person who owned a little sheep under one year of age or without permanent teeth. 10a1aMary held a little sheep under one year of age or without permanent teeth in a position of disadvantage. 10b1aMary tricked a little sheep under one year of age or without permanent teeth. 121bMary gave birth to a young antelope. 122aMary is (or was) the mother of a particular small, gentle person. 133aMary ate a little of the flesh of lamb. 142cMary bribed a small person trading in securities who was easily cheated.

68. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 68 Gause & Weinberg, 1989 What to Do About Language Ambiguity  The Ambiguity Poll - create a measure that requires a solid understanding of the problem to estimate.  Memorization Heuristic - get various individuals to try to recall the problem statement from memory. Parts that are not clear are likely the most ambiguous.  Key Word Technique - determine the key operational words in the statement and list their definitions. Mix and match to determine different interpretations. (Use these terms for glossary.)  Emphasis Technique - emphasize different words until as many interpretations as possible are discovered.  Other Techniques - use other techniques, pictures, graphics, formal methods -- that’s what use cases are for!

69. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 69 Exploring Ambiguity: An Observation Techniques that reduce ambiguity in an SRS often decrease understandability and alienate customers and users. Our goal is to find the “sweet spot” where we attain the greatest understandability with the least ambiguity Understandability Ambiguity The sweet spot

70. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 70  Use natural language for most of the specification  Write as clearly and concisely as possible  Use pictures, diagrams, and dialogs to further illustrate the intent and features of the application  Augment with use cases and other formal techniques to fully define the functionality Ambiguity vs. Understandability: What to Do?

71. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 71 ref - IEEE 1993 Ranked by importance SR103 SR172 SR192 SR71 SR63 SR172 SR103 SR63 SR71 SR192 Ranked by stability Qualities of an SRS: Ability for Ranking  A Requirements Specification is able to be “ranked” for importance and stability if  Each requirement in it has an identifier to indicate the importance and stability of that particular requirement

72. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 72 IEEE 1993 - The system supports up to 1,000 simultaneous users - The system shall respond to an arbitrary query in 500 msec. - The color shall be a pleasing shade of green - The system shall be user friendly - The system shall export view data in comma separated format Qualities of an SRS: Verifiable  A Requirements Specification is “verifiable” if:  Every requirement in it is verifiable. [… to a degree that convinces everybody!]  There exists some finite, cost-effective process with which a person or machine can check that the product meets the requirement Are these requirements verifiable? If not, what is a better way to state them? (Involve QA folks to help decide)

73. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 73 IEEE 1993 Qualities of an SRS: Modifiable  A Requirements Specification is “modifiable” if:  Its structure and style are such that any changes to requirements can be made easily, completely, and consistently, while retaining the structure and style.  Features to facilitate modifiability Well organized Table of contents Index Cross references Minimum redundancy

74. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 74 ref - IEEE 1993 Qualities of an SRS: Traceable  A Requirements Specification is “traceable” if:  The origin of each requirement is clear and each requirement can be referenced in future development Backward traceability (to previous stages of definition or development) Forward traceability (to all documents spawned by the SRS)  Hints: Make sure every requirement is referenceable Use unique numbers Use labels Use “shall" or other unique identifiers Use a requirements repository to maintain traceability

75. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 75 Qualities of an SRS: Understandable  A Requirements Specification is “understandable” if:  Both the user and supplier communities are able to fully comprehend the requirements stated in it  Hints:  Early document should focus on general description and features of the system  Requirements writers must understand both audiences  Use cases can help with understanding the system’s functional requirements and boundaries

76. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 76 Adapted from Alan Davis What Is Not in an SRS?  Design - How to accomplish the requirements  Design Model specifies sub-components of a system and/or their interfaces with other sub-components  Verification - How you’ll know the requirements have been met  Test Model specifies test cases and test procedures  Project Data - When the requirements will be met  Software Development Plan specifies schedules, verification and validation plans, and configuration management plans

77. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 77 Review: Refine the System Definition 1. What is in a software requirement specification? 2.What are the properties of a use case? 3. What is the purpose of the flow of events in a use case?  Who is it written for?  What does the basic flow describe?  What are some different types of alternative flows? 4.What are pre- and post-conditions?  When should they be used? 5.What is the purpose of the “Special Requirements” of a use case? (Continued  )

78. Requirements Management with Use Cases v2000 Copyright © 1998, 2000 Rational Software, all rights reserved 78 Review: Refining the System Definition 6. What are some types of non-functional requirements?  Where should they each be specified? 7.Is your industry bound by legal or regulatory requirements?  If so, what types of specifications should be written to assure compliance? 8.What is a design constraint? Where is it documented? 9. What are some measures of a high quality software requirement specification? 10. What is not included in an SRS?