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Further reading □ Foreword □ Contents □ Preface □ Prologue □ Acknowledgements □ Participants □ 1. Introduction □ 2. Control Structures □ 3. Syntactic Structures □ 4. Cognitive psychology and interaction □ 5. Visual Communication □ 6. Presentations □ 7. Working Groups □ 8. Group Reports □ 9. Postscript □ 10. Position papers □ 10.1 Anson □ 10.2 Baecker □ 10.3 Bo □ 10.4 van den Bos □ 10.5 Crestin □ 10.6 Dunn □ 10.7 Dzida □ 10.8 Eckert □ 10.9 Encarnacao □ 10.10 Engelman □ 10.11 Foley □ 10.12 Guedj □ 10.13 ten Hagen □ 10.14 Hopgood □ 10.15 Klint □ 10.16 Krammer □ 10.17 Moran □ 10.18 Mudur □ 10.19 Negroponte □ 10.20 Newell □ 10.21 Newman □ 10.22 Nievergelt □ 10.23 Ohsuga □ 10.24 Rosenthal □ 10.25 Sancha □ 10.26 Shaw □ 10.27 Tozzi □ 11. Bibliography
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⟶ ACD ⟶ Literature ⟶ Books ⟶ Methodology of Interaction
⟶ ACD ⟶ Literature ⟶ Books ⟶ Methodology of Interaction
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Further reading ⇓

□ Foreword □ Contents □ Preface □ Prologue □ Acknowledgements □ Participants □ 1. Introduction □ 2. Control Structures □ 3. Syntactic Structures □ 4. Cognitive psychology and interaction □ 5. Visual Communication □ 6. Presentations □ 7. Working Groups □ 8. Group Reports □ 9. Postscript
10. Position papers
□ 10.1 Anson □ 10.2 Baecker □ 10.3 Bo □ 10.4 van den Bos □ 10.5 Crestin □ 10.6 Dunn □ 10.7 Dzida □ 10.8 Eckert □ 10.9 Encarnacao □ 10.10 Engelman □ 10.11 Foley □ 10.12 Guedj □ 10.13 ten Hagen □ 10.14 Hopgood □ 10.15 Klint □ 10.16 Krammer □ 10.17 Moran □ 10.18 Mudur □ 10.19 Negroponte □ 10.20 Newell □ 10.21 Newman □ 10.22 Nievergelt □ 10.23 Ohsuga □ 10.24 Rosenthal □ 10.25 Sancha □ 10.26 Shaw □ 10.27 Tozzi □ 11. Bibliography

10.7 A. Paradigm for Task-Oriented Man-Computer Interaction

W. Dzida, S. Herda, W.D. Itzfeldt

Gesellschaft fur Mathematik und Datenverarbeitung

St Augustin

It is emphasized that users of interactive systems are primarily faced with performing their professional tasks. A paradigm for task-oriented man-computer interaction is presented which is assumed to meet major user requirements concerning problem adequate usability and ease of learning. Basic features of the paradigm are formulated in terms of current theories of psychology of learning and performance.

1. Basic concept

Recent investigations on factors of user-friendliness of interactive systems have revealed problem adequate usability and ease of learning to be important design goals (cf. Dzida et al., 1978). Both goals may be achieved by applying two main principles:

The concept favours organizing flexible man-computer dialogues, and thus may meet requirements of different user groups.

We argue that the paradigm may be easily embedded in current general purpose interactive systems.

Structuring users' professional tasks to support user performance and ease of learning

2.1 Decomposing user tasks

Man-computer interaction aims at supporting users in solving their professional tasks efficiently. In a sound task and performance analysis several tasks a user performs at his working place are structured at different levels of abstraction, and described by a tree-structured taxonomy of tasks. Global tasks may be broken down to sub-tasks and to elementary tasks (fig. 1). If the user is able to recognize those tasks he usually is concerned with, the taxonomy of tasks may be regarded to be user-oriented. The taxonomy may be presented by menus at the screen of a display unit.

2.2 Linking user task to system function

Most interactive systems provide user access to system functions by means of a command language. The user must learn a list of commands. Commands are normally names of system functions offered to him by commands corresponding to his task or not.

Instead of this kind of trial and error selection a task-oriented selection strategy should be aimed at the taxonomy. If commands are links between user tasks and system functions the initial mechanical learning step is replaced by goal-oriented and structured learning where each command is embedded in a taxonomy of tasks the user is already familiar with.

STRUCTURE MENU LEVEL 1 STRUCTURE MENUS LEVEL 2 STRUCTURE MENUS LEVEL 3 STRUCTURE MENUS LEVEL 4 USER ACTION LEVEL SYSTEM PERFORMANCE LEVEL TASK 1 • 1.1 • 1.2 • 1.3 • 1.4 TASK 1.1 • 1.1.1 • 1.1.2 • 1.1.3 TASK 1.2 • 1.2.1 • 1.2.2 TASK 1.3 • 1.3.1 • 1.3.2 ELEMENTARY TASK 1.2.2 • 1.2.2.1 • 1.2.2.2 ASSOCIATION SUB-TASK / COMMAND USER-INPUT COMMAND SYSTEM PROCESS FUNCTION ASSOCIATION ELEMENTARY TASK / COMMAND USER-INPUT COMMAND SYSTEM PROCESS FUNCTION

Fig. 1: Taxonomy of tasks represented by menus and commands as links between user tasks and system functions

2.3 Associating user task and command

Whenever a user is going to recognize his task structure (fig. 1, level 1 to 4) he incidentally associates specific tasks with appropriate commands (at level 4). Thus he learns associations. One of the most striking advantages of memory is an efficient method of recall. Association of task and command is assumed to be an efficient method. This follows from the primary law of Associative Memory, the law of contiguity (ANDERSON, 1975).

Three tours in man-computer interaction

For a correct description of higher organisms it is important to distinguish between knowing and doing (SIMON, 1969). In the study of man-computer interaction the distinction between knowing and doing appears as the distinction between learning and task performance. This distinction is paradigmatically represented by the alternative tours direct way and excursion (fig. 2).

STANDARD ACTION MENU DIRECT WAY Information request STRUCTURE MENU DEVIATION stepwise (re-) structuring Return EXCURSION COMMAND system initiated user initiated

Fig 2: Three tours in dialogue (direct way, deviation, excursion)

3.1 Excursion: separating structuring from performing

At the starting-point of man-computer interaction the user has at least two alternatives:

  1. he may submit a command, if he has already learned the association of task and command;
  2. he may request information on a command to perform the action necessary to complete his task.

Both alternatives are presented in the standard action menu>. Other types of actions, e.g. structuring dialogues, are not discussed here.

When submitting a command at the starting-point, the user takes the direct way. His task is then immediately being performed.

By requesting information when the standard action menu is presented, he takes the excursion. There he is informed by structure menus about the user tasks the interactive system is able to support. Before associating an appropriate command with his task the user may refine his knowledge of the system along the structure of his task.

From learning theory we deduce that the user who is just aware of the association between task and command should be forced to return to the starting point of his action (standard action menu). There he may submit the command. For leaving the excursion the user has to press a return key.

3.2 The rehearsal feature

During the return step the user forces himself to refresh the command by reactivating it In his short term memory. This process is called rehearsal. Usually one is engaged in rehearsal when one mumbles a phone number to oneself when going from the phone book to the telephone. ATKINSON & SHIFFRIN (1968) have developed a model with an explicit rehearsal mechanism in short term memory.

3.3 Correspondence between brainware and software

The implementation of an excursion is generally based on principles of the TOTE-Performance Theory (MILLER et al. 1960) and the Steady State System of Conversation Theory (PASK, 1975). The basic ideas are that man is regarded as

These sub-systems, if considered as a whole, may be called brainware. In user-oriented design of interactive systems, the software should be compatible with this structure. For instance, when designing menus and structures for menus one should distinguish

We have observed that some designers of man-computer interaction do not distinguish between doing and knowing. As a consequence of this shortcoming, both the experienced and the less experienced users are dissatisfied with current interactive systems. Therefore, the deviation tour (fig. 2) is assumed to be less effective than the excursion tour for both user groups. This hypothesis, however, has not yet been empirically tested.

Summary

A task-oriented design of interactive systems according to the paradigm would improve users' learning and performance in man-computer interaction. The user is concerned primarily with his tasks. The system designer should establish commands as links between elementary user tasks and system functions. Different tours in dialogue should be separated according to different processes in human task performance.

References

ANDERSON, B.F.: Cognitive psychology. The study of knowing, learning and thinking. Academic Press, New York, 1975

ATKINSON, R.C. & SHIFFRIN, R.M.: Human memory: A proposal system and its control process. In: K.W. Spence & J.T. Spence (Eds.): The psychology of learning and motivation. Advances in Research and Theory, Vol. II, Academic Press, New York. 1968, pp. 89-195

DZIDA, W.: HERDA, S. & ITZFELDT, W.D.: User-perceived quality of interactive systems. IEEE Trans. on Software Engineering, Vol. SE-4, No. 4 (July 1978), pp270-276

MILLER, G.A.: GALANTER, W. & PRIBRAM, K.H.: Plans and the structure of behavior. Holt, Rinehart and Winston. New York, 1960

PASK, G.: Conversation, cognition and learning, A cybernetic theory and methodology. Elsevier, Oxford, 1975

SIMON, H.G.: The science of the artificial. The M.I.T. Press, Cambridge, MA 1969

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