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And identifying the purpose of a softer system means

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defining the requirements for the system. And if you have

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ever done anything like that, for example, we did

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it for the first project in the previous mini course,

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you will know that it is an extremely hard

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task. Identifying the purpose of the software and defining its

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requirements is very, very hard. Why is it so hard?

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First of all, the purpose of most systems is inherently,

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extremely complex, so this has to do with the

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sheer complexity of the purpose of the requirements. Just think

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of how complex is the functionality provided by most systems.

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Second, it is hard, very hard to extract from humans

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this purpose and make it explicit. So, paraphrasing a

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famous quote from the late Steve Jobs, often people don't

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know what they want until you show it to them.

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It's hard to figure out what people really want. Third,

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requirements often change over time. Customers change their

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mind. Designing and building a system raises new requirements.

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So for many reasons requirements tend not to

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be stable, tend to evolve. And that, of course,

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makes it harder to collect them. Finally, for

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any realistic system, there are many stakeholders and they

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often have conflicting goals and requirements. And it

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can be very hard to reconcile the possibly conflicting

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requirements that might emerge in these cases. So for all these reasons,

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it is very, very difficult to

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perform requirements engineering in an effective way.