Soft Systems Methodology - Conceptual Models of Human Activity Systems

Conceptual Models of Human Activity Systems

SSM Conceptual Models of Human Activity Systems (Conceptual Models) are notional, they are not intended to represent what exists but to represent a stakeholder viewpoint. This is often misunderstood. Figure 1 is not intended to represent how rice is, in fact, cooked; but how the stakeholders think it is cooked or how they think it should be cooked or how they would like it cooked.

Conceptual Models take the form of bubble diagrams in which descriptions of activities are enclosed in bubbles and the bubbles linked to each other by arrows. The arrows are intended to represent logical dependency. In Figure 1 the activity "wash rice" is said to be logically dependent on the activities "obtain rice" and "obtain water" being performed. This relation of “logical dependency” is transitive, i.e. if cook rice is dependent on wash rice and wash rice is dependent on obtain rice, then cook rice is dependent on obtain rice. This would appear to conform to what is known, in formal logic, as hypothetical syllogism. However, a connection with logic has been challenged and it has been argued that SSM conceptual models are not “logical” in any sense of the word.

In Checkland's work Conceptual Models are usually limited to a small number (seven, plus or minus two) of bubbles. Also, in fidelity to Cybernetics, the main activities are always supplemented by bubbles representing monitor and control systems. However, in Wilson's Information Requirements Analysis the Conceptual Models may expand to include hundreds of bubbles, and the monitor and control systems are dropped. While the principal SSM authors show a high degree of similarity in their accounts of the early stages of the method, considerable diversity begins to appear at the Conceptual Model building stage.