The purpose of a system is what it does

[turtleyacht]

Related works that mention POSIWID, mostly by W.L. Livingston:

The New Plague (1985)

Have Fun at Work (1988)

Friends in High Places (1990)

Design for Prevention (Silva)

Seeking further references.

[ipnon]

Purpose and function are only different during design.

[amadeuspagel]

This is also true for people.