Dix, Finlay, Abowd and Beale
Chapter 9 - Models of the system
We need to know what a system does in order to assess its usability.
- Standard software engineering formalisms can be used to specify an interactive system. These are of various types:
- model based, such as Z, which describe the system's state and operations
- algebraic formalisms, which describe the effects of sequences of actions
- temporal and deontic logics, which describe when things happen and who is responsible.
- Special interaction models are designed specifically to describe usability properties, including
- predictability and observability, what you can tell about the system from looking at it
- reachability and undo, what you can do with it.
- A full interaction model may be complicated to produce, so we consider an example of a semi-formal, easy to apply technique which
- classifies phenomena as event or status
- embodies naive psychology
- highlights feedback problems in interfaces.
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