Iterative Design

User testing played a key part in the design of Enquire. Because TCL/TK was an interpreted language, and comparatively easy to learn, it could be used for rapid prototyping of design ideas which could then be tested with users.

From an HCI perspective, system evaluation must take into account the following measurable criteria, (from Shneiderman [9], p.X):

• the time needed to learn specific functions,
• the speed of task performance,
• the error-rate,
• subjective measures of user satisfaction,
• users' retention of commands over time.

In addition to these criteria, there are others which relate specifically to the searching task. For ENQUIRE, the following questions exemplified the issues:

• How easy is the interface to use? How good are users at:
  • using the widgets,
  • making use of the help notes at the bottom of the screen,
  • getting to and from the thesaurus,
  • navigating the thesaurus,
  • moving terms into and out of the query,
  • adding new terms with the ``Type Extra Words'' button,
  • navigating between the titles list and the full document display.

• How much do users understand of what is going on? Do they recognize:
  • the significance of thesaurus ``partial matches''
  • the implications of relevance judgements,
  • why extracted terms are added to the current query,
  • when the titles list has changed.

• How do users decide to carry out their search? How do they:
  • formulate their initial query,
  • decide which words and phrases to add,
  • interpret the thesaurus display and functionality,
  • make relevance judgements.

• How do users rate ENQUIRE, and compare it with other systems?

Informal evaluations of the system were conducted with users during the early stages of the design process, resulting in further periods of redesign and debugging. There were also two more structured formative evaluations, which are detailed below. The first took place over three weeks in June 1995, and the second over two weeks in September 1995.