On my own competency

There was a question on programmers.stackexchange.com about whether to put your Stack Overflow reputation in your CV. I don’t, and answered as much: there’s no point in writing for its own sake, unless you want to be a writer. If you want to be a programmer, then you should be a good programmer and any writing you do should be evidence of that.

There’s a great—if somewhat old—resource for evaluating your own capability as a software engineer called the programmer competency matrix. Writing the answer I gave to the above question renewed the memory of the matrix in my mind, so I decided to evaluate myself against it and use that to help build a research and personal development plan.

I’m sharing my own results in this post. My hope is that this will trigger some introspection of your own, and demonstrate just how easy it is to devote a little time to personal development (this took me about an hour to do, including the writing). I’m also being selfish: when I write for publication I’m a lot more organised than if I just push notes into iThoughtsHD or OmniOutliner.

It doesn’t matter whether you agree or disagree with anything I write. If we agree on any row of the matrix, then we’re both pulling in the same direction and pushing the bar a little higher in that area of software engineering. If we disagree, then we’re still both raising the bar, because we both have our special skills that (hopefully) contribute to making the whole industry that bit more skilful and knowledgeable. Of course, if you think that I’m completely brain-dead for choosing not to develop my skills in a particular area, feel free to flame me in the comments.

Notice that it’s hard to be objective about self-evaluation. I hope that my answers below are somewhat accurate, but it’s easy to have an over-inflated opinion of your own competence. In fact, when I was a junior software engineer I felt like I knew more than I do now :). It would definitely be trite to give a nonsense buzzphrase like “we should always be continually improving at everything we’re doing”, because there aren’t enough hours in the day for that. There should be things that we definitely need to work on, things that we “just do” but reflect on how they’re going, and things that we just automatically get on with. Of course, when I think that something should be automatic but I make a mistake, that’s a time to re-evaluate my perception of my skills.

Computer Science

  • data structures: Level 1. I’ve done some study into some of the level 2 features (and even know what some of the words mean in Level 3), but at heart I feel like that’s stuff for a framework programmer to deal with and I’m an applications programmer. I’m happy to believe that the framework engineers know how to implement List<Integer> or NSArray properly and leave them to it.
    Related tale: I once had an interview where the interviewer drew a list on the whiteboard, and asked how I’d sort it. I wrote a "[" at the beginning, and " sort];" at the end. I didn’t get the job.
  • algorithms: Level 2. Again this is largely the domain of the framework engineer, but there are times when it’s become important to my own work such as when I’ve had to do performance engineering (and of course cryptographic algorithms factor heavily into my work). I tend to address algorithmic problems on a case-by-case basis, and don’t feel the need to explicitly schedule some research time.
  • systems programming: Level 2. I do believe that I need to develop here, particularly in the areas of JIT compiling and interpretation. If BDD and DDD (and, to some extent, OOP) have taught us anything, it’s that there are great efficiency savings to be made by expressing a software problem in a way that’s understandable by, or at least explainable to, the user. And that means Domain Specific Languages. I’ve actually seen that work very well, when I was working for Diamond Light Source. Scientists could write working prototypes in a Jython-based DSL that would then either be cleaned up by engineers or reimplemented in the core engine.

    Of course, BDD and DDD are both also examples of RDD (Résumé-Driven Development), but that doesn’t mean they have nothing to offer us.

Software Engineering

  • source code version control: Level 3. To be honest I think that the matrix is outdated here, and that DVCS is well on its way to becoming the new established workflow. When the matrix was written, SVN was the de facto standard for VCS. Version control is just one of those things that you need to know and need to use properly. It will probably still change quite a lot (I don’t think that any of the DVCS platforms out there make the uber-common “star” distribution any easier than decentralised development), and my opinion is that I need to be good at the tools I need to use. Of course, being a contractor that often means being good at all of the tools.
  • build automation: Level 3. I’ve written here before about setting up tools like HeaderDoc and CruiseControl. I definitely think some of the tools need improving, so could find time to work on that.
  • automated testing: Level 3. Something I need to do more of, and can “learn on the job” while I’m doing that: but there isn’t any point in having a “do UI testing” research project.


  • problem decomposition: Level 3. That’s not to say I’m completely perfect at object-oriented analysis and design, and every time I see someone else’s code I’m interested in what patterns they’ve chosen, and how they’ve organised their code. Actually, my current writing project—a book, video training course and several conference talks on TDD—has been useful for learning more about decomposition and modularity.
  • systems decomposition: Level 2. This is an area I definitely need to focus on, because almost all modern applications are actually multiple-component systems that either do, or should, present the same data across multiple devices and feature both dedicated and incidental online components.
  • communication: Level 3. I think the amount of time I’ve spent recently on books, conference talks, workshops and the like means that I’ve actually over-engineered this aspect significantly and can dial back on it once my current obligations are discharged.
  • code organisation within a file: Unsure. Maybe level 3: well I definitely have a style I use and am comfortable with: is it “beautiful”? Does that even matter? Shouldn’t the important factor be: “reading this programmer’s code doesn’t get in the way of understanding and modifying this programmer’s code”?
  • code organisation across multiple files: Level 2. Who uses the file system any more, anyway? I organise my classes and other resources in the Xcode project navigator. Turns out I use Xcode as some sort of “project builder” tool, not the Finder. If the view of projects and groups in the IDE were the metric in question, then I think I’d be at Level 3 here.
  • source tree organisation: Level 2, for similar reasons.
  • code readability: Level 3. Again, this book/research project on TDD has been my most recent and valuable guide.
  • defensive coding: Level 3. Ensuring you don’t only code and test the happy path is one of my current rants, if you give me enough beer. There was a section in my first book on this.
  • error handling: Level 3. I think this is really just an aspect of defensive coding, though I agree that a consistent approach across projects is important. I’m not a person who avoids using exceptions in Objective-C code.
  • IDE: Level 2. I suppose if you count shell script build phases as ‘custom macros’, then I’ve done level 3 work, but I don’t have a library of those shell scripts that I carry around to various projects. I probably could make some efficiency savings by recording how I use Xcode and reducing any commonly-repeated steps or actions.
  • API: Level 1. No, srsly. I know of the existence and capabilities of many of the Cocoa and Cocoa Touch APIs (with, for obvious reasons, the most focus on Foundation and Core Foundation) but always have to look up the class reference docs. This is really the most important thing I need to work on, so my next research project will be to deepen my knowledge of the APIs.
  • framework: Level 2. In addition to the Cocoa frameworks, I’ve worked with WebObjects, Eclipse RCP, wxWidgets and (more’s the pity) Swing. Not sure I particularly need to write a framework at the moment, there are other people who do good jobs of that. Exploring MonoTouch would be useful.
  • requirements: Level 3. Being a contractor, it’s important to know when to try and change the client’s mind and do things differently, if you want to write good software rather than write crap for a good hourly rate. I’ve also worked on in-house teams where the product manager or architect didn’t have any Mac experience, and it’s impossible to work on those without being able to suggest improved requirements.
  • scripting: Level 2. Yes, automating common developer tasks is still in its infancy, and I probably should find, clean up and publish some of the scripts I’ve created over time.
    (By the way: different scripting languages are useful for different things. I’ve learnt a lot of bash, perl and python, but should probably pick up ruby too. Don’t dismiss any of them for looking like unintelligible spider scrawl; you’ll probably find a use for it one day.)
  • database: Level 1. EOF and Core Data do exist for a reason…to be honest I don’t think I’ll ever be a Level 3 database person, it’s probably cheaper to hire somebody if I ever need that. Most of the products I’m currently being asked to work on either have somebody else for that or don’t have strong performance requirements.


Actually, I’m going to skip this section. I don’t believe that you can do a research project on improving your experience; only your exposure. You gain experience by doing.


  • tool knowledge: Level 2. As I’ve said there are clear shortcomings in the tools I’ve used, and I’d love to improve them or write something new and get it out there.
  • languages exposed to: Level 2. I have done Prolog, but no concurrent programming languages. Additionally, Andre Pang’s talk on Functional Programming at NSConf 09 showed that I could learn a lot more from that arena.
  • knowledge of upcoming technologies: Level 3. It’s a particular point of professional pride to me that I know what’s coming up and how it changes what I’m working on. Of course, in a world of non-disclosure agreements then “sharing” has to be limited to immediate project teams and people at WWDC. You are coming to WWDC, right?
  • platform internals: Level 2. I’m not Amit Singh. I already have a project on the horizon to do some more hacking on Clang, and have spoken about that before at NSConf Mini. It’s questionable whether a deep understanding of the platform internals is necessary, or whether that should be abstracted by the platform frameworks and interfaces. Personally I believe it is something useful to know, particularly in diagnosing bug reports. It’s well known that almost no bugs reported in your software are really bugs in the OS, and a deep understanding of the OS can help to confirm that.
  • books: Level 1, because I haven’t read Peopleware. I’ve written 1.5 books, does that count for anything?
  • blogs: Level 3. You’re reading it. As identified above, I probably expend more effort on communication than is necessary.

So, that’s my current state of competency in a nutshell. From there, it looks like my priorities for research goals over the upcoming year or so should be:

  1. Improve breadth and depth of API knowledge
  2. Investigate systems decomposition of a smartphone/desktop/internet system.
  3. Learn how to create and support DSLs
  4. Write and publish improved developer support tools

OK, your turn: what are yours?

About Graham

I make it faster and easier for you to create high-quality code.
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