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Software Architecture cheat sheet

For the past several weeks I’ve been focusing my efforts on learning how to approach software architecture. Despite my experience in developing several applications, I wanted to read and learn more about this to do a better job in the future, for our upcoming project.

I’ve read some articles and a couple of books on this topic. My goal was to extract relevant pieces of knowledge with the final goal of producing one sheet of paper with the most important points. I wanted to stick it onto the wall behind my screen, so that I could refer to it with only a glance. It had to have the most important questions that I should ask myself before committing to anything important during software design.

Today, I finally condensed all I wanted to write, prepared this page, printed and glued it to the wall:

I’ve prepared a PDF that you can download and print to put in your workplace, if you like this.

Here are the points and their explanations:

Is this a “Good Idea”?

I took this one from: Avoid “Good Ideas”

The really insidious thing about “good ideas” is that they are “good.” Everyone can recognize and reject “bad” ideas out of hand - It’s the good ones that slip through and cause trouble with scope, complexity, and sheer wasted effort incorporating something into the application that isn’t necessary to meet the business need.

In other words, think if this is actually necessary or is it just feature creep. Software complexity increases exponentially so having twice the features makes the code complicated by much more than twice.

DRY. Don’t Repeat Yourself

DRY is a well-known software design principle. Explained in Pragmatic Programmers, it means that “Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.”

I already have an ingrained instinct about DRY. Still, I wanted to have a good in-the-face reminder so as not to forget it in a middle of a passionate idea.

Orthogonal?

In other words, how independent is this module or block from other parts of the system? Modularity in software is important. It makes life easier later. It’s easy to understand and easy to overlook.

Testable?

Think how you will test this part of the system. Is it designed in such a way that makes testing easy? Testability depends on modularity, complexity, code style. Don’t neglect testability of your system or code. Testing is important. Manual testing is good. Automatic testing is much better.

Is there another way?

This is also from Pragmatic Programmers. It contains good quotes in every chapter. Here’s one by Emil-Auguste Chartier — “Nothing is more dangerous than an idea if it’s the only one you have.”

Often, when thinking about problems we come up with a solution and run to implement it, feeling happy that we have one. Unfortunately, often the first solution won’t be the best. Think again, be creative, try a different approach. When you come up with more ideas, it will often be the case that the first one was too rushed and that the next ones are, in fact, much better.

Costs of changing this later

Consider the decision you’re about to take. What will it cost you to change it at later stages of the project? Can you defer this decision? If you’re not sure about the decision, can you design the system in such a way that changing it later will not break things and cause unnecessary work?

What if I didn’t have this problem?

This one is from Don’t Be a Problem Solver.

Because architects tend to immediately enter problem-solving mode, we forget, or rather have never learned how, to interrogate the problem itself. We must learn, like a telephoto lens, to zoom in and zoom out, in order to ensure the question is really framed properly, and that we’re not merely accepting what we’re given.

Instead of immediately working to solve the problem as presented, see if you can change the problem. Ask yourself, what would the architecture look like if I just didn’t have this problem? This can lead ultimately to more elegant and sustainable solutions.

What are facts and assumptions? Document rationale.

The last two are from Challenge assumptions - especially your own.

Best practices in software architecture state that you should document the rationale behind each decision that is made, especially when that decision involves a trade-off (performance versus maintainability, cost versus time-to-market, and so on)…

This practice is valuable because by way of listing these factors, it helps highlight assumptions that the architects may have that are affecting important decisions regarding the software that is being designed. Very often these assumptions are based on “historical reasons”, opinion, developer lore, FUDs…

In other words, if you’re designing software architecture, write down why specific decisions are made and then think what of these are facts and what are assumptions. Check your assumptions.

Facts and assumptions are the pillars on which your software will be built. Whatever they are, make sure the foundations are solid.

Download the PDF with these question to stick on your wall.

Jacob.
I’m @apparentsoft both on Twitter and on App.net.

Filed under software archtecture tips cheet sheet

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    Ez szerintem nem rossz.
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    In other words, how independent is this module or block from other parts of the system? Modularity in software is...
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