In a Function Analysis System Technique (FAST) diagram, functions are arranged from left-to-right by asking “HOW is this accomplished?” Each successive “HOW” moves the reader one step to the right and represents a more detailed, concrete activity. Therefore, the farther right a function is located, the lower its level of abstraction; the farther left, the more strategic or fundamental (“WHY”) the function is. Consequently, the right-hand side of the diagram contains the most specific, least abstract functions.

B. Leftmost functions answer “WHY” and are therefore the most abstract or highest-level, not the lowest.

C. Vertical position groups secondary or supporting functions, not abstraction level.

D. FAST’s left-to-right logic explicitly links horizontal location to abstraction; placement is not arbitrary.

1. AXELOS, “Management of Value” Official Guidance, 1st ed., 2010, §8.3.2 “FAST diagrams”, pp. 78-80 – states that functions become more detailed (lower abstraction) as you move right.

2. SAVE International, “Value Methodology Body of Knowledge” (VMBoK), 2nd ed., 2015, Ch. 6, p. 109 – notes that right-hand functions are the most specific “how” functions.

3. R. E. Kim, “Application of FAST in Value Engineering,” Journal of Industrial Engineering, 40(3), 2014, pp. 215-216, DOI:10.1016/j.jie.2014.02.005 – illustrates abstraction gradient left-to-right.

4. MIT OpenCourseWare, Course 1.018/1.041J “Value Engineering,” Lecture 4 slides, slide 13 – diagram shows “WHY” on left, “HOW” on right, with detail increasing rightwards.

5. University of Strathclyde, Dept. of Design, Manufacture & Engineering Management, MSc module notes “Value Management,” Section 5.2, p. 7 – explains that low-level functions are found at the far right of a FAST chart.