Applying Cognitive Psychology to System Development - Fundamentals and Assessment Tools for Occupational Ergonomics - page 523

. Also for efficiency, decisions can be made about how deep to go in the hierarchy. In some cases,
lower levels can be left out if they are judged to be unimportant in terms of predicting critical
behaviors
Two final ways to increase efficiency in completing such a cognitive walkthough are to:
. Only represent those portions of the goal hierarchy that are judged to be critical by the
analyst
. Limit the number of use cases to be considered based on some judgment of importance, for
instance, considering only those use cases that are likely to occur frequently, that could result in
some highly undesirable outcome, or that are relevant to some design decision about which the
developers are uncertain (Mitta et al., 1995)
Example of Step 3. Identify the state of the product and the associated “world” at each node. Previously,
we have illustrated the completion of Step 1 (Select a use case for evaluation) and Step 2 (Specify the
normative paths for this use case). To complete the third step, we need to identify the screen displays
associated with each node in the hierarchy represented in Figure 24.3 and Figure 24.4. (Note that the
rest of the context — the associated “world” — is assumed to stay constant in this illustration, as the
student is accessing the library system at home on her own computer over a high-speed connection,
and that help from a librarian is available only by phone.)
Analysis of a Sample Path. Suppose the student enters “wedding songs” and changes the search type
from the default (Title) to Subject, but uses the default format (All). Figure 24.5 shows the appearance
of the Basic Catalog Search screen for this path, and Figure 24.6 shows the appearance of the search
results displayed for this path.
To complete Step 3, we would normally identify the state of the software interface associated with all
possible paths leading to success in the normative goal hierarchy. For the purposes of this example,
however, we will limit our focus to this one sample path in which the information seeker has started
by entering the term “wedding songs” in a subject search for all possible formats.
Example of Step 4. Generate predictions. The final step is to walk through the hierarchy along each path
that would lead to success, and to play psychologist, generating predicted behaviors at each node (for
FIGURE 24.5 Basic catalog search screen for the sample path: searching for “Wedding songs” with the search type
Subject and the default format (all).