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So, let's look at these three characteristics one by
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one. Scalability for software architecture is its ability to handle
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the growth of the software system. For example, for a
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web based system, scalability could be the ability to handle
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a larger workload by adding new servers to the system.
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Scalability is therefore an important characteristic of a software architecture,
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especially for the kinds of systems that can grow over
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time. So, we're going to mark it as an ideal characteristic.
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Cohesion is a measure of how strongly related are
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the elements of a module. Clearly, we should shoot
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for high and not low cohesion when developing a
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system. We want to develop modules whose elements cooperate to
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provide the specific piece of functionality rather than modules
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consisting of a bunch of elements that provide different
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unrelated pieces of functionality. Therefor, low cohesion is definitely
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not something that we want. We want high cohesion instead.
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As for coupling, coupling is a concept related to cohesion
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and is also a measure. In this case though, it
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is a measure of how strongly related are the different
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modules in a system. Low coupling, which is often correlated with
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high cohesion, is an important and ideal characteristic of a
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software architecture as it indicates that the different modules in
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the system are independent from one another. Each module provides
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a specific piece of functionality and it can provide it without
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relying too much on other modules.
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Basically, systems characterized by low coupling
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and high cohesion, are systems that are easier to understand, and to maintain.
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