Design Pattern: ID(5) Zooming


The operator would like to work at multiple levels of detail of alarm information. He wouldn't need to see such levels simultaneously.


The human operator needs to move rapidly and fluidly between levels of detail of alarm information.


Support focused and contextual views based on zooming, which involves a temporal separation between these views. Zooming is based on a camera analogy; the action is analogous to changing the focal length of a camera lens. It is possible to magnify a decreasing fraction (or vice versa) of an element under the constraint of a viewing frame of constant size. Zoom-in is similar to moving closer to an object while zoom-out is similar to moving further away from it. Because the size of the display screen is fixed, the effect of zooming-in is to show a smaller area of the display page at a higher magnification; the effect of zooming-out is to show a larger area at lower magnification.

Known uses
Fig1.Diagram of different elements of a nuclear power plant provided by the GoalArt control system
Fig1. Applying zooming techniques to the Catapult iPower SCADA operational environment for electric control room SCADA

Zooming facilitates two different cognitive tasks. With zooming-in, extraneous information is removed from the visual field, perhaps resulting in a more manageable view, whereas zooming-out reveals hidden information, often context that is already known but perhaps cannot be recalled. It often allows a user to rediscover their location in an information space and to integrate a new context within a mental model. (Card, S. K., Mackinlay, J. D., & Shneiderman, B. (1999). Readings in information visualization: Using vision to think Morgan Kaufmann Pub. )