Functional Decomposition

≈ 38 min

Functional Decomposition

Functional decomposition describes what a system must do, then splits that overall purpose into smaller functions — without committing prematurely to which components will deliver them. Functions are written as verb-noun pairs ('store water', 'limit current') because a verb-noun pair describes a job, not a part, which keeps many possible components available for the concept-generation stage that follows.

Worked example. "Design a borehole pump" jumps straight to a component. Decomposing the function first — sense water level, move water upward, store water, prevent dry-running — leaves each sub-function open to several possible technologies (a float switch or a pressure sensor can both 'sense level').

Core checkpoint: Write functions as verb-noun pairs such as 'store water' or 'limit current', not as component names.

Which statement best captures the core checkpoint for writing a function in a decomposition?

Write functions as verb-noun pairs such as 'store water' or 'limit current', not as component names.

Write functions as brand names so the correct part is obvious later.

Skip writing functions and list components directly to save time.

A function and a component name are interchangeable, so either works.

Functions in a decomposition are written as pairs of what two parts of speech, such as 'store water'?

Which of the following is written correctly as a function, not a component?

Limit current

A resistor

The blue wire

Circuit board version 2

A student decomposing a rainwater-harvesting system writes: 'use a first-flush diverter'. What is the strongest revision, and why?

'Remove initial contaminants' — this states the job, leaving open whether a diverter, filter or settling tank performs it.

No revision needed — naming the diverter is precise and saves time later.

'Buy a diverter' — this adds a purchasing step to the function list.

'Water system' — a shorter label is always a better function.