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Unfortunately, extracting requirements from these sources is not
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a straightforward task, as there are many issues involved
3
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with the requirements elicitation. One first problem is the
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thin spread of domain knowledge. Knowledge is rarely available
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in an explicit form, that is, it is
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almost never written down. Moreover, knowledge is often distributed
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across many sources. For example, in the graphical depiction
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here, to find out that this is the purpose
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of the project. The developer, the analyist, needs to talk
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to a lot of different people. And, to make things even
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worse. There are often conflicts between the knowledge gathered from
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different sources. A second issue is the fact that the knowledge
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is often tacit. What is also called the say, do
14
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problem. In the example shown here. For instance. We have a
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customer that is describing to the analyst. The way in which
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he accomplishes a task. So it performs these three steps and
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reaches the goal. Whereas in practice, the actual way in
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which this task accomplished is by going through a larger number
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of steps to get to the same goal. So the point
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here is that, even if the knowledge were more concentrated, so
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not as spread as in this example. People simply find
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it hard to describe knowledge that they regularly use. So it
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is hard to make this knowledge explicit, to pass this knowledge
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to someone else. Yet another
25
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problem is limited observability. Identifying requirements
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through observation is often difficult as the problem owners might be
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too busy to perform the task that we need to observe.
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Or they might be doing a lot of other things together
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with the task that we need to observe, so that becomes
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confusing. That introduces noise. Moreover, even when this is not the
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case, the presence of an observer might change their problem. It
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is very typical for human subjects to improve or modify an
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aspect of their behavior, which is being experimentally measured in response
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to the fact that they know that they're being studied. You know
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that somebody's studying you and you change the way in which you behave.
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A typical issue. Finally, the information that we collect might be biased.
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For several reasons. People might not feel free to tell you what you
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need to know. Or, people might not want to tell you what
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you need to know. For example, in all the common cases in which
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the outcome might effect them, people might provide you a different picture
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from the real one. In order to influence you. So, they might have
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a hidden agenda, and mislead you, either
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consciously or unconsciously. So, all these issues
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add to the complexity of collecting requirements,
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of identifying the purpose of a system.
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