The human activity system is a notional purposive
system which expresses some purposeful human activity, activity which could
in principle be found in the real world. Such systems
are notional in the sense that they are not descriptions
of actual real-world activity (which is an exceptionally complex phenomenon)
but are intellectual constructs; they are ideal types for use
in a debate about possible changes which might be introduced
into a real-world problem situation (Checkland, 1993: 314).
