Human-Computer Interaction 3e Dix, Finlay, Abowd, Beale
CHAPTER 17
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.
- Most formal models and notations focus on events and changes that happen
when they occur, but we need richer models to deal with:
- interstitial behavior - the things that happen between events such as
dragging an icon
- physical objects in ubiquitous computing or virtual reality
- the tension between precise time and more fuzzy human ideas of time.
