yoked-state space hypothesis
The claim that users of representational devices (such as computer systems) need to mentally represent the device itself, the domain to which the device refers, and the way in which the device represents the domain. See Payne, Squibb, and Howes (1993).
A particular notation for formal specification developed principally at Programming Research Group Oxford University. It is based on set theory, with mechanisms to allow large specifications to be separated into parts and structured. See Spivy (1988).
Models that can make a priori predictions of quantitative performance of users on an interactive system. The are called zero-parameters because no parameters need to be set from data collected on the system in question; all numeric parameters can be set through a task analysis and pre-existing data from prior research.
zone of proximal development
The inventory of capabilities people can currently demonstrate with assistance (human and material support) and therefore may, in the future, be able to achieve by themselves.
It is a figure of speech in which a word or phrase literally denoting one kind of object or idea is used in place of another to suggest a likeness or analogy between them (defined by Merriam-Webster online dictionary). Designers of graphical user interfaces often use well know objects as interface metaphors to give users an indication of how interface objects will behave. For example, an image of a trash has been adopted to indicate the operation of deleting files.
Notice metaphors can be non-visual, such as in the saying "surfing the web." Here the word surfing is a metaphor.
It is usually a pictorial representation (Merriam-Webster online dictionary). An icon can be a metaphor when such a metaphor is appropriate. When a metaphor cannot be found for an icon, the design of such an icon will take special effort in term of user testing.
Human short term memory
It has been shown that humans' short term memory contain 7 plus or minus 2 units. That is, it is not very big. In addition, short term memory is really short.
user interface prototype
an operational version or mock-up of a system that supports interaction between the user and the system that is used for user testing and iterative design
a user interface control (e.g., a menu or scroll bar), often predefined by the windowing system used to build a user interface
software agents that are interact with the user using natural language and that are often given a human-like appearance