CASSM project

Introduction p3: the 'misfit' concept

A highly-usable, highly successful IT-based device must succeed in many ways. One way it must succeed is by matching the concepts built into the device with the concepts held by the intended users. If users think about songs, the device should deal in songs, not in individual notes.

The concepts must be available and usable at the interface between the user and the system; and if the user changes something, it should not result in unexpected changes to other parts of the device that are not visibly related. (Consider what happens when you change a cell in a spreadsheet - almost anything could happen anywhere else in the sheet.)

Every real device is a balance between the competing demands of perfection and real-world constraints - so it is important to know how far off-balance we might be. CASSM investigates the degree to which a design fits the concepts of intended users.

In that respect it is rather different from previous User Evaluation Methods which have paid little attention to conceptual mismatch.

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This page last modified 26 February, 2010 by Ann Blandford