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We just saw two of the three distinguishing aspects of

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the rational unified process. The fact that it is used

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case driven and the fact that it is architecture centric.

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The third and final distinguished aspect of R.U.P. is that

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it is iterative and incremental. So let's see what that

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means by considering the lifetime of a software project. Basically,

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the lifetime of a rational unified process consists of a

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series of cycles, such as the ones that are represented here.

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Cycle one, cycle two, through cycle n. And as

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you can see, these cycles can also be called increments.

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And each one of the cycles involves all of

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the main phases of software development. In addition, each cycle

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results in a product release which can be internal

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or external. More precisely, each cycle terminates with a product

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release that includes a complete set of artifacts for

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the project. That means code, manuals, use cases, non-functional

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specification, test cases, and so on. So, I've just

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said, that each cycle involves all of the main phases

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of software development. Specifically, each cycle is further divided

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in four phases. Inception, elaboration, construction and transition. In a

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minute, we will look at each one of these

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phases in detail and see how they relate to the

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traditional activities of software development. Before that, I want

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to mention the last level of these iterations, which happens

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within these individual phases More precisely, inside each of these

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phases, there might be multiple iterations. So what are these

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iterations? Well, basically, each iteration corresponds to a group of

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use cases that are selected so as to deal with

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the most important risks first. So if you have a

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set of use cases that you're considering, which means that

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you have a set of features that you need to

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implement, you will select for each iteration the most risky

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ones that you still haven't realized, and realize them in that

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iteration. And then continue in the following iterations with less and

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less risky ones. So basically what happens in the end is

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that essentially each iteration extends

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the functionality beyond the previous iteration.