The diagram provided is a Function Analysis System Technique (FAST) diagram, a key tool in Value Methodology’s Function Analysis phase, as taught in the VMF 1 course (Core Competency #2). FAST diagrams map the relationships between functions of a system, with the horizontal axis showing the “how-why†logic (critical path) and the vertical axis showing supporting functions. Functions are classified as basic, secondary, required secondary, or higher-order based on their position and role in the diagram. According to SAVE International’s Value Methodology Standard, “the basic function is the primary purpose of the system, typically found on the critical path; higher-order functions are the reasons why the basic function exists, located to the left of the basic function; secondary functions support the basic function and are often vertical; and required secondary functions are necessary to achieve the basic function.â€
In the FAST diagram:
The critical path (horizontal, marked by Y in an earlier question) runs from E to F to G to J to L to M to N to O, representing the main sequence of functions.
Scope lines (B and D) define the study’s boundaries, as identified in Question 15.
Function E is positioned at the far left of the critical path, just inside the left scope line (B).
In FAST diagramming:
Thebasic functionis the primary purpose of the system, typically located near the center or right of the critical path within the scope lines. Here, it would likely be a function like J or L, which is central to the system’s purpose.
Thehigher-order functionis the reason “why†the basic function exists and is located to the left of the basic function, often at or near the left scope line. Function E, being the leftmost function on the critical path, answers “why†the subsequent functions (F, G, etc.) exist, making it the higher-order function.
Secondary functions(e.g., S, T, U, K) are vertical, supporting the critical path, and are not on the main horizontal sequence.
Required secondary functionsare secondary functions essential to the basic function, but E is on the critical path, not a vertical supporting function.
Thus, Function E, as the leftmost function on the critical path, is thehigher-order function, representing the overarching objective or need that the system fulfills.
Option A (Secondary Function) is incorrect because secondary functions are off the critical path (e.g., S, T, K), while E is on the critical path.
Option B (Required Secondary Function) is incorrect because E is not a secondary function; it is on the main path, not a supporting vertical function.
Option C (Basic Function) is incorrect because the basic function is typically more central on the critical path, not at the far left.
Option D (Higher Order Function) is correct, as E’s position at the left of the critical path indicates it is the higher-order function, answering “why†the system exists.
[:, SAVE International, VMF 1 Core Competency #2 (Function Analysis), which includes the use of FAST diagrams to classify functions as basic, secondary, or higher-order., SAVE International, “Value Methodology Standard,†section on Function Analysis, describing FAST diagramming conventions, including the positioning of higher-order functions to the left of the basic function., ]