Separating your Concerns

I spent a lot of time debating what I should title this post. Should it be “Buzz Words”? Or maybe “Separation of Concerns and SRP”… SOLID Concerns? In the end, I settled on this — Separating your Concerns. I also spent a bunch of cycles, asking myself what I really wanted to cover. What ideas do I want to convey? Then I spent some time thinking about how I would convey that message. What literary road would I take? From whom’s style would I borrow. However, none of this is of concern at this moment. The fact that it’s written is all that matters now.

I want you to think about the word, Organization, and what it means to you. Just take a moment to reflect on it.

When I think about Organization, I think about form, and about order. Organization makes me think about neatness, about cleanliness, and about space. Room to breath, and room to work. Organization to me is logical, it’s order — and the opposite of that is chaos, and anarchy. In our world, spaghetti.

Hold that thought.

Now, I want you to consider what “programming” is. What exactly is it for? What is a programming “language” for? Be specific.

You might think to yourself — “programming is telling the computer what to do.” Kind of. “A programming language is the syntax we follow to do that.” Kind of.

One of the definitions of “programming”, is the act of providing a computer (or machine) with with coded instructions for the automatic performance of a task. Now, that’s the definition of programming. But anyone who has worked on any project bigger than a hobby project, with multiple developers, knows it’s so much more than that.

Programming, not only is about telling the machine what to do. It’s doing it in a way that other people can understand it. It’s almost as if our programs are stories, and the compiler is the translator that turns it into instructions. The programming language, therefor is our medium of communication, between developers. Since, realistically the computer can’t understand C++ or C# directly. Consider for a moment, if we all had to “program” in CPU instructions written in binary, something a computer can understand directly. As soon as you have more than one person on the project, you’ve got a nightmare. It would be enough that the person has to communicate with the computer in that way, let alone with other developers. Trust me when I say, programming in higher level languages is for us, not them.

You might say “No. Comments are for communicating with other developers, and code is for the computers.”, to which I would reply simply “You’re wrong.” If you think that, I am sorry for you. (Actually, I’m more sorry for people who work with you.)

So programming, then is really a form of communication. It’s not completely unlike writing a story. This may seem like a bit of a Woo-Woo metaphor, but it helps to illustrate my point. Your tangled rats nest of notes you took in school, might’ve served its purpose for your studying. Though, it’s highly unlikely that it is of any value to anyone else. Not unlike programming, just because something is working when you write it, doesn’t make it of value to anyone else. Unfortunately, that mess of notes you took 3 years ago, is probably of little value now, even to you. The realistic truth, is that you then, is not you now. This is just like bad code. Trust me, I know because I’ve written so much bad code it’s mind boggling.

It’s not like this wasn’t a problem with writing. That’s why people invented literary tools, sentence structure, paragraphs. That’s why we have archetypes, and plot patterns. It’s to better communicate our stories. These things exist in programming, we have numerous languages, different patterns and practices. Hell, we even have smells. All these things try and make our code more easy to understand, for others, and for ourselves.

Let’s go back to Separating of Concerns, and how any of what I just wrote actually applies to programming. If we stick with the metaphor, that coding is a lot like writing, then what in writing is “Separation of Concerns”? Well, in your travels I’m going to assume you’ve read a book. In that book might’ve been a Table of Contents, that Table of Contents laid out the chapters of the book. The ‘Logical Separations” in the book. The book is structured in such a way, that the chapters flow. The author has taken the time to logically bundle pieces of relevant information. Can you imagine reading a book that is teaching you about Botany, and in Chapter 1 they dive directly into the root structure of a Hibiscus, and on the next page the configuration of soil nutrients? That’s not a book I want to read. So the act of bundling relevant information, for consumption of the reader, is in fact “Separation of Concerns”. Now, you can take this further. Do you think that when the author is crafting her book, that she’s worried about what type of paper it’s going to be printed on, or the font size? Probably not. Though — if she’s writing a book that contains needs special paper and tiny font,  likely she will ensure that the printing process will indeed support her special paper and tiny font. She certainly isn’t going to worry about this while she’s writing the book. In this regard, the author is Separating Concerns, regarding her functional requirements i.e. writing the book, and the non-functional requirements that the book needs to be on special paper in tiny font.

If we consult Wikipedia in regards to “Separation of Concerns”, we can look at the statement from Edward Dijkstra, that probably coined the term.

Let me try to explain to you, what to my taste is characteristic for all intelligent thinking. It is, that one is willing to study in depth an aspect of one’s subject matter in isolation for the sake of its own consistency, all the time knowing that one is occupying oneself only with one of the aspects. We know that a program must be correct and we can study it from that viewpoint only; we also know that it should be efficient and we can study its efficiency on another day, so to speak. In another mood we may ask ourselves whether, and if so: why, the program is desirable. But nothing is gained —on the contrary!— by tackling these various aspects simultaneously. It is what I sometimes have called “the separation of concerns”, which, even if not perfectly possible, is yet the only available technique for effective ordering of one’s thoughts, that I know of. This is what I mean by “focusing one’s attention upon some aspect”: it does not mean ignoring the other aspects, it is just doing justice to the fact that from this aspect’s point of view, the other is irrelevant. It is being one- and multiple-track minded simultaneously.

The first time I read this quote, I don’t think I fully groked it. So I read it again. And again. And again. Then I remembered a term that a lot of developers will preach. Make it work. Make it good. Make it fast. Coined by Kent Beck, in the UnixWay we’ll go with sometime ago. But Dijkstra beat him to it. Kind of. The common theme here, is that these pieces are logically separated. You concern yourself with the correctness, the efficiency, and the functionality of your application each in isolation. All the while, keeping in the back of your mind the other concerns. It was eye opening.

Alright — enough philosophy. How does that actually affect my programming?

Well we know now, that Separation of Concerns is essentially grouping logically functions of our program. That allows us to worry about a certain function of our application, without flooding our minds with other pieces. It allows you to focus. I don’t care how smart you think you are, you can’t focus on more than one thing at a time. If you try when you’re programming, you’ll end up with a tangled mess. You’ll start to bring pieces that belong in other areas, into the area you are. Then you’ll take pieces from where you are, and put them in areas they don’t belong. The smartest people, have the innate ability to focus on one thing at a time, while keeping track of all the other things outside.

While authors have chapters. As programmers we have abstractions. In my opinion, the two definitions that most closely apply to programming are:

the process of considering something independently of its associations, attributes, or concrete accompaniments.


the quality of dealing with ideas rather than events.

The first part of an abstraction, is that it lets you consider the component devoid of its baggage. You don’t care that it references EntityFramework, Boost 1.61, or the entirety of  GitHub. You don’t care that it has 1.3 million member variables, and 42 private functions. The only thing you care about is that it fulfills its contract to you. That is, you care about it’s public API. You ask for a list of Foo, you better get a list of Foo. That’s why you need to keep your public API clean and concise. Because that’s your first layer of abstraction.

The second definition, and an extremely important part of an abstraction. Is that it allows you do deal with a concept, rather than its details. This lets you think at a higher level, and deal with larger concepts without drowning in all the details. The (not so) modern remote or clicker on a television, had an abstraction that allowed you to press “up”, and that would tune the frequency of the television to the channel. This allowed you to work with the idea of “up” and “down” on your remote, to tune your television. Instead of being concerned with the tuning of the radio frequency that represents the channel.

Obviously given the fact that this entire post is riddled with metaphors, you might already know I’m a sucker for metaphors. The good news is, I’m about ready to unveil the pièce de résistance, of my metaphors. It’s the one I think most clearly buttons this concept up. It’s the car. The car, isn’t just a fantastic example when we’re teaching inheritance. It’s just a great all around metaphor when it comes to programming.

Specifically the steering wheel — this is a fantastic abstraction metaphor. You get into your car, and you look at the wheel. Do you care about the mechanics behind it? No. Do you care about the linkages between the wheels and whatever makes them turn? Nope. How about the power steering pump? The electronics? Nope, and Nope. You care that this thing makes your vehicle go left and right.

Do you know why this is so important when it comes to driving? It’s because driving is complicated, you need to have quick reaction times, and be able to focus on other things, like the rules of the road. At that level, you only have the capacity to concern yourself with “left” and “right” when it comes to steering. Imagine what driving would be like, if you had to push and pull leavers and rotate gears to turn. It would be a nightmare. That wheel in the cockpit of your vehicle, allows you to focus on actually driving, instead of the details of turning the wheels. It moves that concern to a different area. Now, do the mechanics behind that wheel still matter — hell yeah! But as long as they’re functioning when you’re driving, it isn’t your concern. It’s beautiful. The second benefit of this, you can drive a bunch of different cars. You could have a beat up pinto today, and tomorrow be “rolling ‘benz”, all because you know how to use a steering wheel. Steering stays the same, and it has for many years.

Another awesome benefit of the steering wheel, debug-ability. Say you crash your pinto taking a turn. Pretty easy to figure out where the bug is. Is the bug between the seat and the wheel, or the wheel and the head lights? Let’s check, when I turn left, do the wheels turn left? Yes. Is it the correct amount? Check. Okay — problem lies between the wheel and the seat. Easy.  It’s also really easy to check this when the car comes off the lot, or after you’ve had it serviced. Weird — that sounds a lot like unit testing to me.

So in order to sum all of this up. Separation of Concerns affects the entire spectrum of software development, from architectural design, right down to the details of the code. It’s about organization, and only concerning yourself with one topic at a time, all the while keeping in mind those other pieces. You first concern yourself with the design of your program. Capture the like ideas, divide them into chapters. While you’re implementing your chapters, look for steering wheels. Let your chapters flow into one another, but don’t mix Chapter 1 and Chapter 13.  Find spots for steering wheels, don’t force them to use gears and knobs. Mostly — know that this is a process, and it’s hard. You’re likely not going to get it right the first time. It’s just about trying, keeping these concepts in the back of your mind, and looking for opportunities to apply them.

I hope that this post has brought some light to the topic of Separation of Concerns. Maybe next time I’ll try my hand on one of the other concepts of Computing that I got wrong so many times.

“Organizing is what you do, before you do something, so that when you do it, it is not all mixed up” — A.A. Milne

I hope you have a splendid day, and as always — Happy Coding!




Separation of Concerns

Make it work, Make it Right, Make it Fast

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