CHI '95 ProceedingsTopIndexes
TutorialsTOC

Models, Prototypes, and Evaluations for HCI Design: Making the Structured Approach Practical

George Casaday, Cynthia Rainis


George Casaday
Digital Equipment Corporation
110 Spitbrook Road
Nashua, NH 03062
casaday@usable.enet.dec.com


Cynthia Rainis
Digital Equipment Corporation
200 Forest Street
Marlboro, MA 01752
rainis@meta.enet.dec.com

© ACM

Abstract

Designing human-computer interaction can be a large and complex task. One way to manage that complexity is to divide design into smaller interrelated subcomponents; this is called the structured approach. It is an excellent way for a beginner to learn design and for a team to stay on track while doing design. However, there are some difficult parts of the structured approach that must be handled for the approach to be practical: A good selection of subcomponents must be made, the relationships among them must be taken into account, and effort must be allocated to them in balance. This tutorial teaches a robust, practical, and learnable route to the structured approach for designing human-computer interaction.

The tutorial offers examples, templates, and practice on a specific set of design artifacts called intermediate work products and a process for creating and evaluating them in practical team design. The presentation is accessible to beginners but the techniques are taken from real practice and can be applied immediately.

Keywords

Design process, structured design, modeling, prototyping, formative evaluation.

STRUCTURED APPROACH TO HCI DESIGN

Definition

The structured approach divides the HCI design process into distinct but strongly interrelated components so a design team can focus upon them individually. This contrasts with the holistic approach, which treats all aspects of design from requirements to look and feel as an inseparable unity. The recent textbook of Preece et al. [7] discusses the complementary use of both approaches.

Advantages

The structured approach has definite advantages over the holistic approach in certain circumstances. Therefore, having a structured approach in the personal tool kit is advantageous for designers and consultants, especially when there is a strong need to establish credibility or when a convincing public rationale is needed for design decisions. The approach is well suited to situations where an incremental strategy is required or where support for holistic or participatory design approaches is lacking.

Problems

There are problems with working through a sequence of work products. For example, it is easy to get stuck in working out an early intermediate work product in great detail and never get on to others (analysis paralysis). Or it is easy to make errors in the early work products and have too little time to correct them when the consequences are revealed later (the big bang problem). Another problem is that there may be schedule adjustments or a need to demonstrate progress that can embarrass a design that is caught with only the first intermediate work products done.

MAKING THE STRUCTURED APPROACH PRACTICAL

The tutorial offers several templates and techniques for overcoming the problems of the structured approach while preserving the advantages. For example:
  1. * Seven specific intermediate work products spanning the full HCI design space.
  2. * Small intermediate work products can be completed in a day or two.
  3. * Relationships among work products and an effective sequence for creating, evaluating, and revising them.
  4. * Evaluation against specific usability requirements: learnability, relearnability, efficiency, error behavior, and subjective satisfaction.

DESIGN STRATEGY

To help beginning designers organize the creation and evaluation of a sequence of intermediate work products, this tutorial suggests a design strategy that can be summarized as follows:
  1. * Plan on several passes through the sequence
  2. * Work sequentially (or approximately so) through all the intermediate work products
  3. * On each pass keep the level of detail about the same for each intermediate work product
  4. * Formatively evaluate (Hix & Hartson, Developing User Interfaces [2]) each as it is created to improve quality but not to add detail
  5. * Each pass through the sequence, design in more detail.

INTERMEDIATE WORK PRODUCTS

Usability Requirements Specification The usability requirements specification is the foundation for all that follows. It includes at least:
  1. * A definition of users.
  2. * A qualitative statement of the relative importance of each of the five usability dimensions: Consult Nielsen's Usabilty Engineering [5].

Scenarios

A scenario (as we are using the term for today) is a short story of a specific actor, in a specific situation, doing a specific sequence of actions with our imagined system. Scenarios are an effective way for a design team to communicate an understanding of how an imagined system is going to work. Look under "use cases" in Object- Oriented Software Engineering, by Jacobson [3].

Work Models

A work model is an abstract representation of the activities that can be performed by users of the imagined system to achieve their purposes. Work models are an essential means for the design team to summarize, the complexity of the imagined system. Read the chapter on Dynamic Modeling in Rumbaugh's Object-Oriented Modeling and Design [8] as well as task hierarchy topic in Zemke's Figuring Things Out [9].

Storyboards

A storyboard visually shows a specific sequence of actions with our imagined system. Storyboards are a good way to communicate the essentials of how a user will get work done with a system, especially for stakeholders who want a summary. See Film Directing Shot by Shot, Katz [4].

User Interface Map

A user interface map is an orienting graphical layout of the user interface components, "navigation" paths, and information flows. It provides an essential overview of the whole user interface for the designers. We have no reference for the user interface map, but the general ideas of such diagrams are in Page-Jones' The Practical Guide to Structured Systems Design [6].

Paper Prototype

The paper prototypes presented in the tutorial are quickly built simulations of the imagined system designed to "run" at about half the speed of an on-line system when operated properly. They are specifically designed to get early user feedback and engage users in participatory design. Paper and on-line prototypes are presented by Andriole in Rapid Application Prototyping [1].

On-Line Prototype

An on-line prototype created in a rapid prototyping tool. (Visual Basic for the tutorial) is a useful transition to final testing and implementation. See [1] for a discussion.

TUTORIAL ACTIVITIES

  1. * Introductory lecture to explain concepts for the day.
  2. * A case study with worked out examples called Willow Tree Inn Visit Management System is supplied.
  3. * Working in small teams, participants modify or add to each of the work products in the case and evaluate them using several techniques. Instructors coach.

References

  1. 1. Andriole, Stephen. J. Rapid Application Prototyping, QED Technical Publishing Group, Boston, MA, 1992.
  2. 2. Hix, D., and Hartson, R.H. Developing User Interfaces: Ensuring Usability Through Product and Process. John Wiley & Sons, New York, NY, 1993.
  3. 3. Jacobson, Ivar. Object-Oriented Software Engineering. Addison-Wesley, Reading MA, 1992.
  4. 4. Katz, Steven D. Film Directing Shot by Shot. Michael Weise Productions, Studio City, CA. 1991.
  5. 5. Nielsen, Jakob. Usability Engineering. Academic Press, New York, NY, 1993.
  6. 6. Page-Jones, Meilir. The Practical Guide to Structured Systems Design. Yourdon Press, New York, NY, 1980.
  7. 7. Preece, J., Rogers, Y., Sharp, H., Benyon, D., Holland, S., Carey, T. Human-Computer Interaction. Adios- Wesley. New York, NY, 1994.
  8. 8. Rumbaugh, J., Blaha, M., Premerlani, W., Eddy, F., Lorensen, W. Object-Oriented Modeling and Design. Prentice Hall, Englewood Cliffs, NJ, 1991.
  9. 9. Zemke, R., Kramlinger, T., Figuring Things Out. Addison-Wesley, New York, NY, 1982.