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In our initial definition of requirements engineering, we talked about
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software systems. But what do we really mean when we
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use the term software? Software is an abstract description of
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a set of computations that becomes concrete, and therefore useful, only
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when we run the software on some hardware, and that,
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in the context of some human activity that it can
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support. So what does that mean exactly? What that means
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is that when we say software, what we really mean is
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a software intensive system. That is, the combination
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of 3 things, the software, the hardware on which
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the software runs, and the context in which the
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software is used. Just to illustrate, let me show
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you this through a picture. What I'm showing here
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is a customer, a user, that is using, is
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accessing, an ATM machine. And this action involves several
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things. There is the software that drives the logic
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of the ATM machine. There is the hardware on
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which the software runs. And there is the context
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In which the software is used. And in this
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case, the context is the bank. And only by
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considering these 3 things together can we really understand
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the functionality that is represented here. So the bottom
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line here is that we usually take hardware and
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context for granted in this equation. But they actually
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need to be explicitly considered when building a
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system. Otherwise, we might forget this is all
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the functionality, and ultimately of the requirements. And
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we might end up with the wrong system.
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