Text & Gesture Interaction and Inference

Question 1

Interaction principles

Answer 1

How does the user get content into digital form?

How does the user navigate around the content?

How does the user manipulate the content?

Question 2

Principles of Direct Manipulations

Answer 2

Objects that are of interest to the user should be continuously visible in the form of a graphical representation on the screen.

Operations on objects should involve physical actions

Actions that a user makes should be rapid, should offer incremental changes and should be reversible.

The effect of actions should immediately be visible so the user knows what has happened

There should be a modest set of commands doing everything that a novice might need, but it should be possible to expand these, gaining access to more functions as the user develops expertise.

Question 3

nomodes

Answer 3

The same action should always have the same effect. This wan’t in the case within editors such as vi because hitting a key could have different consequences at different times.

Question 4

Deixis

Answer 4

Sentences in which the object is identified by pointing at it rather than naming it.

Question 5

Substantial innovations achieving deixis

Answer 5

• WIMP interface - Windows, Icons, Mouse, Pointer

* Placement of text characters between characters rather than identifying a single character.

Question 6

Fitts’ law

Answer 6

An experimental observation of the time it takes to point at a given location is related to the size of the target and also the distance from the current hand position to the target.

T = K lg(A/W + 1) where A = amplitude, W = width.

It can be difficult to establish the constant with new pointing devices. This constant is sometimes called ID or the Index of Difficulty.

Question 7

Keystroke Level Model

Answer 7

Counting the individual actions needed to carry out a particular task, including the number and extent of mouse motions as well as all the keys pressed on the keyboard.

Question 8

Goal Operators Methods Selection

Answer 8

Comines keystroke-level estimates of user actions with an AI planning model derived from work on Generalised Problem Solver. The GPS operated in a search space characterised by possible intermediate states between some initial state and a goal state. Problem solving consisted of finding a series of operations that would eventually reach the goal state.

Two heuristics are recursively applied:

• Selecting an intermediate goal that will reduce the difference between the current state and the desired state.
• if there’s no operation to achieve that goal directly, decompose it into sub-goals until the leaves of sub-goal hierarchy can be achieved by individual keystrokes or mouse movements.