The purpose of a system is what it does

Related works that mention POSIWID, mostly by W.L. Livingston:<p><i>The New Plague</i> (1985)<p><i>Have Fun at Work</i> (1988)<p><i>Friends in High Places</i> (1990)<p><i>Design for Prevention</i> (Silva)<p>Seeking further references.

Purpose and function are only different during design.

This is also true for people.