21.4 User-centered design

2 1.4.1 The Users

2 1.4.2 The Tasks

21.4.3 The Information Space

These first two terms are relatively self-explanatory, but infonnation space is a more vague term, by which is meant the document, database, texts, and so forth on which the user works (see 26.5.2). An information space could therefore be as small as a single text fragment or as large as an on-line database, national archive, or university library. It is the presence of a boundary rather than the size or number of items which defines the concept. The information spaces currently in existence are numerous (just think of all the types of documents that are available in the paper domain), but these are likely to be overrun with new forms of information space in the hypermedia world when graphics, sound, video, and immersive graphics eventually appear. Information type can be shown to interact with both users and tasks; i.e., people utilize information differently depending on its type, their experience, and what they want from it (Dillon et al., 1989).

21.4.4 The Centrality of Context

Of course all tbree basic factors come together to provide some contextthe scenario in which certain users interact with particular information to perform specific tasks (see 12.3.1.2) . In embracing user-centered principles for design, it is essential that the contextual variables are clearly specified. A doctoral student and a solicitor may both be searching an on-line database for references to relevant material, but one may be looking for any relevant item while the other may be looking for a specific supporting case. To assume that this is the same task, or that these users are equivalent and could be supported by the same system would be simplistic and lead to the sort of confused reasoning that posits "hypertext is better (or worse!) than paper." Such statements betray a naive acceptance of commonality of purpose and ability on the part of all potential users and is almost certain to lead to lack of usability in systems design.

21.4.5 Usability and Hypertext

Jonassen (l990) recognizes the central connection between hypertext design and user requirements: "The most significant problem in creating hypermedia is deciding how to structure the information. The answer to this question depends, in part, upon how the hypermedia will be used" (p. 12). Wright (1990) also supports a strongly usercentered approach to hypertext design for educational applications. In response to the rhetorical question as to "what really matters?" in hypertext design, she gives an unequivocal answer: "The answer will nearly always depend upon the task that the learner is engaged in. This task will determine the functionality required by the learner . . ." (p. 171).

For some learning tasks, minimal requirements might seem obvious: CD-quality sound for poetry and language students, high-resolution screens for students of the visual arts, and large-format screens for designers. Yet even these would hardly ensure learning and at best could only be considered the starting point for a user-centered design. However, for many learning contexts the functional requirements are not even that specifiable, particularly when interface and information structures are at issue. The only solution is a fine-grained task analysis that cannot only determine the functionality but also the particular instantiation that is most appropriate for the range of users. As Wright points out, there are often many ways in which a function can be providedjust think of the number of ways in which a database can be searched.

The microcomputer has been justifiably celebrated as a real general-purpose tool. Ironically, the hypertext designer may have to constrain the computer in order to empower the user. While the computer can be programmed to undertake highly complex transformations on abstract data structures, the majority of users are more inclined to think in terms of simple transformations on more "concrete" or familiar data structures.

It may seem that we are arguing for a different hypertext instantiation for every learning context based on a new and detailed task analysis. Without a backward look at existing user models of data structures, this would probably be a recipe for chaos. Evidence for this suggestion comes directly from the evolution of our most successful information technologythe printed book.

We have had nearly 500 years experience of using printed textbooks, and they not only support a wide range of applications but users also have such a strong mental model of their generic structure and organization that they can successfully adopt an equally wide range of usage strategies. What we understand as the book's standard structure, both physical and organizational, evolved over time, and readers' models also developed and accommodated these changes. However, the enduring success of the book as an artifact is largely due to a faithful adherence to common user expectationschange took place but only very slowly.

While it is clear that hypertext can support activities impossible or very difficult to perform with paper, we must be sure that we introduce such designs in order to improve our support of, or to enable, valid learning tasks. It is not sufficient that we can browse a million pages on our desktop, or link 100 articles together for rapid retrieval at the click of a mouse button: such capabilities/are only important in terms of their utility to human learners. Yet there are few signs that most learning scenarios require such support, and little knowledge on how we might best provide it in terms of usability, even if it were required.

21.4.6 Beyond Media DifferencesInformation Structures and Knowledge Representation

It is clear that readers form mental representations of a paper document's structure in terms of spatial location (Lovelace & Southall, 1983) and overall organization. Dillon (1991), for example, has shown that experienced academic journal readers can predict the location within an article of isolated selections of material from it with a high degree of accuracy, even when they cannot read the target material in detail. Such representations or models are derived from years of exposure to the information type or can be formed in the case of spatial recall from a quick scan of the material. Such models or superstructural representations (van Dijk & Kintsch, 1983; see 5.3.7) are useful in terms of predicting where information will be found or even what type of information is available. Consideration of existing models is vital in the design of new versions so as to avoid designing against the intended users' views of how the information should be organized.

The qualitative differences between the models readers possess for paper and electronic documents can easily be appreciated by considering what you can tell about either at first glance. A paper text is extremely informative. When we open a hypertext document, however, we do not have the same amount of information available to us. We are likely to be faced with a welcoming screen that might give us a rough idea of the contents (i.e., subject matter) and information about the authors/developers of the document, but little else.

Hypertext may appear to be a completely new presentation format and therefore free to establish new user models based on the radically new technology. Unfortunately for the creative system designer, the current generation of potential users approach the new technology with expectations that are grounded in print. This is not surprising when the primary content of most hypermedia systems is, and may well continue to be, text. It may be electronic rather than printed, but that can be a minor difference to the user.

Some researchers have accepted this legacy and constructed hypertext systems that rest heavily on not only the conceptual structure but the physical format as well. Benest's (1990) hypertext system employs a realistic onscreen representation of an open book with pages that can be "turned." The system was not designed, or developed, with the benefit of empirical studies, but it is intuitively appealing and an impressive achievement in its time.

In contrast, the SuperBook developed at Bellcore and described comprehensively by Landauer et al. (1993) has benefited from exhaustive user studies (see 30.11.1). SuperBook incorporates a number of familiar print conventions but does not attempt to reinvent the printed book on screen. Instead, development effort has been directed to enhancing the application's intelligent features in a manner that users can employ effectively. In comparative trials, SuperBook has proved superior to printed texts in terms of speed and accuracy for search-type tasksbut only after repeated tests and redesigns on the basis of those tests (see 12.4.1.2).

What is important to note is that experienced readers have acquired expectations of how information spaces are organized, and we need to be aware of this in our designs. It is precisely because such models of information are often ignored that we read so much of the navigation problem for users of hypertext (see Dillon, McKnight & Richardson, 1993).