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Ambiguity and Specificity

Ambiguity and Specificity. Steve Chenoweth & Chandan Rupakheti Chapters 23, 24 - Requirements Text. Questions 1, 2. Image from http://hardboiledpoker.blogspot.com/2011/03/ambiguous-images.html. Problem. Specification must be easy to understand and must be clear.

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Ambiguity and Specificity

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  1. Ambiguity and Specificity Steve Chenoweth & Chandan Rupakheti Chapters 23, 24 - Requirements Text Questions 1, 2 Image from http://hardboiledpoker.blogspot.com/2011/03/ambiguous-images.html

  2. Problem • Specification must be easy to understand and must be clear. • Balancing the two might be difficult • Must be easy enough for the client to understand • Must be unambiguous for the developers Question 3

  3. Light Box Exercise • After On pushed but before Off pushed system is termed “power on”. • After Off pushed but before On pushed system is termed “power off”. • Since most recent On press if count has been pressed an Odd/Even number of times, Odd/Even shall be lit. • If either light burns out, the other shall flash every 1 second. Even Odd Count Off On Power

  4. On Off Duty Cycle A On Off Duty Cycle B 0 1 2 5 6 3 4

  5. Example No 2 • For up to 12 aircraft, the small display format shall be used. Otherwise the large display format must be used.. Which format is this, anyway?

  6. Example No 3 • Shut off the pumps if the water level remains above 100 meters for more than 4 seconds. Uh oh…

  7. Example No 4 • Create a means for protecting a small group of human beings from the hostile elements of their environment. Your basic hostile element – Empire battle cruiser. From http://www.eawpr.net/units/dreadnoughts/.

  8. Example No 5 • The product shall show all roads near the destination. Good enough?

  9. Example No 6 • The product shall show the weather for the next 24 hours. Required or not?

  10. Example No 7 • When the users presses the L and the R button simultaneously, the alarm is turned off. Ok, which ones are L and R? And, do the burglars know this?

  11. Example No 8 • The doors of the elevator never open at a floor unless it is stationary.

  12. Some problematic statements • Incomplete lists ending with "etc.," "and/or," and "TBD.” • Vague words and phrases such as "generally," "normally. • Passive voice, such as "the counter is set." (By whom or what?). • Words and phrases whose meaning can be disputed between developer and customer, such as • instantaneous, simultaneous, • To the extent practicable, • Where applicable

  13. Which one do you prefer? Or, • The system displays the Basic Loss Information Page, with a form to enter basic loss information specific to the claim line. • The clerk fills out the form then clicks the "Add" button • The system queries the claims database to confirm that there are no existing, possibly competing claims. • The system then assigns an ID to the claim and displays the confirmation page. • The clerk clicks the "Confirm" button, and the system saves the claim, then triggers acknowledgement to be sent to the agent. • The clerk enters basic loss information specific to the claim line. • The system confirms that there are no existing, possibly competing claims and assigns a claim number • The clerk confirms they are finished; the system saves and triggers acknowledgement to be sent to the agent.

  14. Techniques for Disambiguation • How do we detect it? • Memorization technique • Emphasis technique or Keyword Technique • How do we avoid it? • Use natural language if possible • Use pictures and diagrams to illustrate intent • Communicate – When in doubt ask? • Augment with technical specs Questions 4,5

  15. Technical Methods for Specifying Requirements • Finite State Machines Start Question 6

  16. Technical Methods for Specifying Requirements • Decision Tables and Decision Trees

  17. Technical Methods for Specifying Requirements • Entity Relationship Diagrams • In Milestone 3 the platform team will develop an ER diagram.

  18. Technical Methods for Specifying Requirements • Pseudo code • What is it? • For each function’s that results from an use case, you must provide the following information • Name • Arguments • Return Type • Pseudo code • Develop an architecture diagram. Finish Question 6

  19. 374 Transition • The strategic thing is for all of you to be in the same section of CSSE374, to avoid having to switch to a different project! • We will devise some system to make this possible! Your ideas are welcomed…

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