Interaction Styles

Overview

To frame our discussion, consider:

What are the major interaction styles fo human-computer interaction in use today?

On what dimensions could we compare and constrast these styles?

Is usability attainable in system development?

OUTLINE

Idiot Proof

History

Different terms have been used to describe the communication between the user and the computer (software). As richer styles of communication have become commonplace interaction styles has become the term of choice.

Command

Early applications were command-driven. Users were expert, knowledgeable and not afraid of computers. They could be expected to overcome any obstacles by sheer perseverance.

Commands provide a way of expressing instructions to the computer directly. Communication between user and computer is purely textual.
Commands can take the form of function keys, single characters, short abbreviations, whole words, or combination of the first two. An issue with command interface is the number of keystrokes required to complete a command.

Commands must be remembered. Care must be taken in choosing the commands for the system.

Form Fill-in

At the other end of the user spectrum from experts in those early days was the clerk. Form fill-in was designed for clerical workers with little experience with computers, to enable them to carry out repetitive data entry tasks. These interfaces mimicked papers forms with the aim of retaining the characteristics of data entry in the paper medium. Navigation from one data entry area to another was designed to allow clerks to move the insertion point without looking at the screen.


Menu

A list of options are presented to the user and the appropriate decision is selected by typing some code or selection the option required. Unlike command-driven systems, menus do not require the user to remember the item they want, they only need to recognize it.

Choose the option desired:
     1 = input data manually
     2 = input data from data file
     3 = perform simple analysis
     4 = perform detailed analysis
     5 = other options
Select Option ?

Pull-Down Menu, Pop-up, Hierarchical


Concerns:

1. Naming of items on the option list

2. Depth versus breadth

3. Categorizing options

4. Time to selection (Fitts Law)

Direct Manipulation

(Windows, Icons, Menus, Pointing)

Direct manipulation systems are characterized by icons representing objects. These objects can be acted upon directly by the user using a pointing device. The choice of icons to represent objects of interest to the user is important. If representations are well-chosen then the learning curve is steep owing to the user's familiarity with the objects and intended actions.

Concerns:

1. The degree of match between the designer's choice of representation and the user's understanding.

2. Choice of metaphors to support the user's activity.

3. Explicit attention to places and ways the instantiated and "real" objects differ.

4. Cultural bias of representation choices.

Which Interaction Style is best?

Measurable Goals

1. Time to learn -
How long does it take for typical members of the users community to learn how to use the commands relevant to a set of tasks?

2. Speed of performance -

How long does it take to carry out the benchmark set of tasks?

3. Rate of errors -

How many and what kinds of errors are made in carrying out the set of tasks?

4. Retention over time -

How well do users maintain their knowledge after set period of time? (perhaps related to frequency of use)

5. Subjective Satisfaction -

How much did users like using various aspects of the system?

Principles in Designing for Usability


(Gould and Lewis, CACM, 28(3), 1985)
"Any system designed for people to use should be easy to learn (and remember), useful, that is contain functions people really need in their work, and be easy and pleasant to use."
(p. 300)

1. Early focus on users and tasks.

Study the cognitive, behavioral, and attitudinal characteristics of the users. Study the nature of the work expected. Suggested concerns are literacy level, reading level, usual length of time at job, ...


2. Empirical Measurement

Users should use simulations and prototypes of the system early in the development process to carry out real work, and their performance and reactions should be observed.

3. Iterative design

Design must be a cycle of design, test and measure, and redesign.

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References