Match the following to their appropriate “How” direction on the function logic path for the...

The correct “How” direction follows the classical FAST logic path from the broader purpose toward the dependent means of accomplishment. SAVE defines FAST as a graphical representation of dependent relationships between functions and states that a Classical FAST model displays function interrelationships using how-why logic . In this eyeglasses example, Improve vision is the higher-order purpose: it explains why the basic function exists. The basic function is Correct vision , because prescription eyeglasses exist primarily to correct the user’s vision. Moving in the “How” direction, the system corrects vision by Position lenses and Secure lenses ; the frame, bridge, arms, and nose pads exist to keep corrective lenses in the proper relationship to the eyes. The farthest “How”/lower-order decision is Select eyeglasses and Select contact lenses , representing the selected means or alternative correction approach.

The distractors are not on the critical function logic path. Secure position and Resist damage are supporting or secondary dependability functions. Complement appearance is a sell/aesthetic function, because it improves user acceptance but does not define the primary functional logic. SAVE’s glossary distinguishes higher-order, lower-order, and secondary functions and explains that secondary functions support the basic function through a specific design approach.

References/topics: Function Analysis Phase; FAST Diagramming; How-Why Logic; Critical Function Logic Path; Basic, Higher-Order, Lower-Order, and Secondary Functions.