On Ambiguity and Specificity 1 Finding the Sweet

On Ambiguity and Specificity 1

Finding the “Sweet Spot” o One of the most difficult challenges in specifying requirements is to make them detailed enough that the can be understood without over constraining the system. o The question most often asked is “to what level of specificity must I state the requirements in order to avoid any chance of being misunderstood? ” 2

Ambiguity Example – “Mary Had a Little Lamb” o What does this sentence mean? o Using the keyword or dictionary technique, we focus on the words had and lamb. o “Had” is the past tense of “have”, so we’ll use the definition of “have”. 3

Ambiguity Example – “Mary Had a Little Lamb” (Cont’d) o have 1 a: to hold in possession as. . . 4 a: to acquire or get possession of: to obtain (as in “the best to be had”). . . 4 c: ACCEPT; to have in marriage. . . 5 a: to be marked or characterized by (to have red hair). . . 10 a: to hold a position of disadvantage or certain defeat. . . 10 b: TRICK, FOOL (been had by a partner or friend). . . 12: BEGET, BEAR (have a baby). . . 13: to partake of (have dinner). . . 14: BRIBE, SUBORN (can be had for a price) 4

Ambiguity Example – “Mary Had a Little Lamb” (Cont’d) o Lamb 1 a: a young sheep esp. less than one year old or without permanent teeth. . . 1 b: the young of various other animals (e. g. , smaller antelopes). . . 2 a: a person as gentle or weak as a lamb. . . 2 b: DEAR, PET. . . 2 c: a person easily cheated or deceived, esp. in trading securities. . . 3 a: the flesh of lamb used as food. 5

Lambic Interpretations “Have” “Lamb” Interpretation 1 a 1 a Mary held in possession a little sheep less than one year old or without permanent teeth. 4 a 1 a Mary acquired a little sheep less than one year old or without permanent teeth. 5 a 1 a Mary is the person who owned a little sheep lest than one year old or without permanent teeth. 10 a 1 a Mary held in a position of disadvantage a little sheep less than one year old or without permanent teeth. 10 b 1 a Mary tricked a little sheep under one year old or without permanent teeth. 12 1 b Mary gave birth to a little young antelope. 12 2 a Mary is (or was) the mother of a particular small, gentle person. 13 3 a Mary ate a little of the flesh of a lamb. 14 2 c Mary bribed a small person trading in securities who was easily cheated. 6