Usability Principles Specific to Interactive Authoring Support Environments
Paula Kotzé
Department of Computer Science and Information Systems,
University of South Africa
P O Box 392, Pretoria
0003, South Africa
ABSTRACT
This poster illustrates an interaction framework and usability principles that can be used in the design and evaluation of interactive authoring support environments aimed at the development of computer-based instructional systems.
KEYWORDS
Usability principles, interaction models, interactive authoring support environments, computer-based instruction.
INTRODUCTION
Abstract principles for effective interaction derived from knowledge of psychological, computational, and sociological aspects of the problem domain can be used to direct the design and evaluation of a product from its onset. Three categories of general usability principles can be identified (Dix et al. 1998) -- learnability(including predictability, synthesizability, familiarity, generalizability, and consistency), flexibility(including dialogue initiative, multi-threading, task migratability, substitutivity, and customizability), and robustness(including observability, recoverability, responsiveness, and task conformance).
However, in defining these principles it is easy merely to provide general and abstract definitions that are not very helpful to the designer. The principles should be combined to form a close bond with the specific paradigm and application domain under consideration.
Authoring support environments (ASEs) are used to develop interactive multimedia applications. They are widely advocated for the development of computer-based instructional (CBI) material. ASEs can be divided into three main groups according to the interface approach they follow -- display-based, map-based and code-based. This poster presentation suggests a framework of principles which, if adhered to, would lead to more usable interactive ASEs for the CBI development domain, and would support the different paradigms on which these authoring approaches are based. The focus is on the principles that could support authors in achieving their goals, as well as the flexibility of the ASE in supporting different authoring approaches.
INTERFACE FRAMEWORK
The interface framework (Kotzé 1997) used in defining the usability principles is specifically geared towards interactive ASEs and the development of CBI material. It consists of a process involving the relationships between four state sets -- the internal state of the ASE, the display state of the ASE, the resulting CBI state, and the CBI display state. The internal state space of an ASE refers to the functional state of an ASE during the authoring process, while the display state space refers to the external perceivable renderings of the ASE. The CBI result state refers to the state of the CBI
system under construction, while the CBI display state refers to the way in which the CBI system will be rendered to the 'learner' in the delivered product.
A model based on a combination of a modified version of the Sufrin and He (1990) framework and the global state approach of the interactors framework of Duke and Harrison (1994), is used as basis for the interface framework.
USABILITY PRINCIPLES
The specific usability principles addressed include different levels of object content observability and object structure observability, dynamic and static displays, distinguishable object renderings, representation multiplicity, equal opportunity displays, and task migratability.
Each principle is illustrated by means of a formal definition using the interface framework and the Z notation, as well as an example from an existing commercial ASE. A set of functions linking certain internal and display states is used in defining the various usability principles. There is, for example, a principle known as media content observabilitywhich aims to assist the author in determining the 'appearance' of the instructional content as well as the manipulation thereof. This principle is defined as a function between the Media_Stateand the Media_Displaystate, constrained by its relation to the Media_Resultand Media_Result_Display states via the renderand result_rendermappings:
REFERENCES
Dix, A., Finlay, J., Abowd, G., Beale R. (1998),Human-Computer Interaction,
Prentice Hall Europe.
Duke, D.J., Harrison, M.D. (1994), Connections from A(V) to Z. Technical Report
System Modelling/WP21, AMODEUS II Project, ESPRIT Basic Research
Action 7040.
Kotzé, P. (1997), The use of formal models in the design of interactive authoring
support environments, DPhil Thesis, Computer Science, University of York. Sufrin, B., He, J. (1990): Specification, refinement and analysis of interactive
processes, inby M.D. Harrison and H.W. Thimbleby (eds.),Formal Methods in
Human-Computer Interaction,Cambridge University Press.
