For the problem of converting a number of quarts to the corresponding number of liters, the task of writing requirements likely is easy.

• Must indicate language for writing the specifications (e.g., English, Unified Modeling Language, etc.)
• Must decide accuracy of input expected and output required
• Should indicate how large or small the numbers might be; what range of values are anticipated?

General Problem Specifications

Goals:

• Clarify the problem, to include all relevant details
• Indicate what results are wanted
• Want completeness: all cases clarified from a user's perspective
• Want clarity (no ambiguity): all parties should agree completely on what should happen
• Want consistency: there should be no inconsistencies

Practice

• Omissions, ambiguities, inconsistencies common
  • Example 1: When trouble arises in a distributed system, one component may expect input data to be resent but the other component may not have the capability to resend
  • Example 2: Ballistic Missile Early Warning System, 5 October 1960
    Source: "Moon Stirs Scare of Missile Attach", New York Times, 8 December 1960, pp. 71-72.
• Example 3: Write a complete specification for riding a bicycle
  • Identify all relevant conditions
  • Remember to include the opening of a car door when riding through city streets with curb-side parking

created 3 January 2007 last revised 7 January 2007

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