Expressing
Specifications
lThree
ways to formalize what the user wants in terms more suitable for engineering design and
analysis
»Prescriptive specifications (or constraints)
–Specify values for attributes of the designed product/process
–Ex.: The
ladder step length can not exceed 20 in.
»Procedural specifications
–Identify specific procedures for calculating attributes or behavior
–Ex.: Maximum
bending stress on a step is computed from smax = Mc/I and the step is safe if smax does not exceed sallow
»Performance specifications
–Identify performance levels that signify the desired functional behavior has been achieved
–Ex.: A
step on a ladder is safe if it supports an 200 kg load