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I'm going to conclude this set of examples with
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a system that you might also know, Bash. And in
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case you don't, Bash is a Unix shell written as
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a free software replacement for the traditional Bourne shell, also
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called sh. So what I'm showing here is the
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descriptive architecture of the command component of Bash. So, is
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the architecture, as implemented, of the command component of Bash.
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And the component is the one here sort of highlighted
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in gray. And what you can see here, these names are
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the sub components of the command component. And if we look at
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this architecture, two design problems of the component can kind of jump
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at us. The first one is the lack of cohesion within the
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component. So, if you look here, you can see that only
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a few connections exist between the sub-components. And having a low cohesion
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is normally not a good thing for a design. The second thing
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that we can note is the high coupling. The component has tons
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of connections with other components. They're, these edges that are
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leaving the components and going towards other parts of the system.
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So basically, this component has low cohesion and high coupling, which
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is exactly the opposite of how a good design should be.
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Given the structure, it is clear that anytime you change
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this component you might need to change a bunch of other
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components in the system. And of course, when changing other components
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in the system, you might also need to chance the command
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component as well. And along similar lines, to understand this
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component you probably need to look at many other parts of
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the system, which is also less than ideal. And one
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important point here is that with all these examples, I'm not
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really trying to criticize any specific system, what I'm trying
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to show instead, is how complex software architectures can be, and
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how much they can degrade over time. And this is true
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for most systems, not just the ones that I showed you.
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