How to improve your open source code (5) - Planning of an Application or Library

This post was written during my trip through Iceland and published much latern than it was written.

In this and also maybe in the next few articles we will focus on rather code-related things than on direct code properties. I hope that’s okay.

Planning of an application or library is not easy, not at all. But how much planning do we actually do before writing code? And should we do more?

My thoughts on the subject.

What we’ve learned

One that has studied computer science should know at least some UML types like class diagrams, flow charts, module plans and use case diagrams. They are used in (let’s call it) “normal” software development and in the professional world out there.

But when we are developing open source software for our own needs and maybe for our friends, we do that often in our chambers at home. Class diagrams are often not being developed and I can say that I never saw a hobby programmer draw a use case diagram before writing the code of the application.

Why we don’t use it

Why is that? Well, because open source software is often done as a hobby type of thing, there is often no need for planning ahead. A hobbyist is able to hold use case, simple class diagrams and flow charts “in his mind” because he has great knowledge of the domain.

In fact. as he defines the domain entirety, he is both stakeholder, project leader, software architect, programmer, tester and marketing guy at the same time. He knows what problems are about to be solved and therefore can adjust every aspect of the application to the needs required.

This holds true for small and medium sized applications or code bases, where the problems is of certain complexity but not too big. Basically one could say that every aspect of the domain has to fit into one head without much effort, in the open-source-programming-at-home-world. With a bit of training, I believe, one can even get to a point where only a few aspects of the domain have to be in a persons mind to be able to work on a solution

But there is certainly a point where the effort needed to solve a specific problem explodes. One can still write software to solve the problem at hand, but not in reasonable time.

So why don’t we hobby programmers do not use planning tools like we’ve learned in university? Why don’t we use diagrams to make things clearer, better documented, even before the real programming starts? The answer is quite simple: because it annoys the hell out of us. We don’t like to plan ahead. We don’t like to adjust plans as soon as we find out that changing a small aspect of our library could be changed to gain more flexibility and overall goodness. We don’t like to check our plans before writing down the next module until it works.

Coding is fun, planning is not.

But should we use these things

In my opinion, this is foolish. We really should use the things we learned in university to plan out software and of course also to document it. It would be such a huge improvement of everything to simply think a bit more about it before actually implementing it!

How we do it

What we do and why we do not use tools to plan ahead is explained with one sentence: We program from the user interface to the implementation, because the other way round is to complicated. Or, with other words: We program top-down because bottom-up needs planning and therefore not that easy.

Of course, I’m speaking about the average case. I’ve programmed bottom-up before but, for me, it seems much more error prone than top-down does, especially without a plan.

Also, I do not say that top-down is not error prone. Not at all. When writing an API without an actual implementation in mind, one easily results in sacrificing cleanness and speed at some points to keep the API nice, which is not always a good idea. So top-down is only good as long as we get it right.


Tooling is one big problem in this context. We do not have a toolchain for planning just yet. At least I do not have one that I would like to use. Because we are really good at controlling (versioning, moving around, managing) our source code (for example with git, and to some extend github), we also want to be able to do this with charts diagrams. But we also want the niceness of SVG-rendered graphics. We don’t want to play around with layout all day long, but use tools to simply get the job done.

And there are no such tools available.

Sure, one can use graphviz to design such things, but then again we do not have a nice overview on what’s going on while editing our work. One could use ascii-art to draw all those things, but hey… ascii-art. We are better than that, aren’t we? We could render the ascii-art into SVG… though the tooling there is not yet as good as it should be. And even if it would be, version controlling these things with git is (I fail to believe otherwise) painful.


Well, I can only conclude the obvious here. We need better tooling for the open source programming community to do their planning, if they need to. Clearly, one does not always have to (or want to) plan things before trying out. But when one does, the tooling should be there and be useful and help with the process.


In the next episode we will talk about version control of open source software projects. I’m not going into details about git or other systems used, but rather on the style how they should be used so everyone is pleased with it. This might be strongly biased, but hey, isn’t this whole article series biased?