The System Image

A triangle of three disconnected vertices (Fig. 1.11):

1. Designer's model — the designer's conception of how the product looks, feels, and works.
2. User's model — the mental model the user develops through interaction.
3. System image — everything perceivable from the built product: its physical structure, documentation, instructions, signifiers, websites, help lines, sales literature.

Central claim: The designer is not present and cannot communicate directly with the user. Therefore the entire burden of communication falls on the system image. The user builds their model only from the system image.

Consequences:

• If the system image is incoherent, incomplete, or contradictory (as with the refrigerator), the user cannot form a correct model and the product fails — no matter how brilliant the underlying design.
• Most important is providing a good conceptual model that guides users when things go wrong.

Confidence

1.0 — explicitly defined with the designer/user/image triangle.

Sources: ["DOET ch.1 'The System Image' p.31-32 (Fig 1.11)"]