June 2010 Edition
Computer Science Department, University of Cape Town
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In the previous unit we looked in a critical way at interactive systems and their development and did not like much of what we saw. In this unit we begin to look at more positive things: solutions.
There are many tools and techniques for designing systems for improved usability, and the question which should immediately come to mind is ‘which is the best?’ The answer is: ‘it depends’. There are many types of interactive systems and many types of users using them for many different tasks. The initial challenge for a developer wanting to make use of these techniques is to find the most appropriate one for the job at hand.
The first major distinction is between ‘design methods’ and ‘summative evaluation methods’. Essentially the distinction lies in when they applied to the interactive system:
during the design process, i.e. before there is a tangible system that has been developed, or
after the majority of the design process has taken place, i.e. when there is an implemented system that can be tested.
There is also a technique known as ‘rapid prototyping’ which aims to occupy the middle ground between design methods and summative evaluation.
We will later present arguments that design methods are preferable, as they should get the major problems out of the system before a costly implementation is produced. Summative methods may identify major problems, but it is likely to be extremely expensive to remedy big problems at this late stage in the design process. Summative methods are still necessary, but should ‘clean up’ small problems with usability such as screen design, while major issues such as fitness for task have been addressed earlier in the design process.
It should be a case of ‘either-or’ for a successful development scheme; to build really usable systems on time and to-budget many of the design and evaluation methods we will describe in this unit will need to be used, but crucially they need to be used well and intelligently by designers. There is not a panacea for usability; no one technique will guarantee a usable system. Many of the techniques that we describe are about identifying usability problems, and structuring the solutions to those problems. How the problems get solved is still left to a great extent to the skill and knowledge of the designers.
There are two techniques for improving the usability of interactive systems: design techniques and summative evaluation techniques. What differentiates the two? Why, in general, is it impossible to evaluate a system for usability during the design process.
Answer to this question can be found at the end of the chapter.
The task artefact cycle describes a common occurrence; namely that a developer produces a tool for a certain task, and then finds that the users of that artefact use it in a completely different way to that expected.
Think of two examples of where you have used a tool in a way that it really was not designed for, one example being a computer application and one from the wider world.
Now think of the tools/computer programs you use at work or home and see if you can think of ways in which you could use them in different ways to how they were intended.
A discussion on this activity can be found at the end of the chapter.