Saturday, August 25, 2007

Online burndown chart generator

One of the aspects of Scrum is its focus on transparency - getting all information out in the open. And one of the areas that enables the transparency is the burndown chart. It's a public posting of the progress of the team throughout its current sprint.

On the horizontal axis you see the days of this sprint. The vertical axis describes the amount of work. At the top of the vertical axis is the number of "ideal man hours" we committed to for this sprint. The straight diagonal line is the "ideal burndown" that we're aiming for. The slightly less straight line is our actual burndown. As you can see this chart is from somewhere during the third week of our four-week sprint and we're slightly above target. But things don't look as desperate as a few days before, thanks to some colleagues getting back from Holidays (which it says in the small scribling that you probably can't read).

As a Scrum master I like to post this information as publicly as I can. So just having it on the wall of our team room isn't good enough, since there are many people that don't visit our team room. Ideally I'd like to have the burndown chart projected on a wall in the central hallway of our office, so everyone can see it first thing they come in in the morning. But as a nice step along the way to this, I chose to publish the chart (and the rest of our product backlog) on our project wiki.

In the first sprints I did this by taking a photograph of the burndown chart every morning, right after updating it. I'd then upload the photo to our wiki. The only problem is... uploading them every day turned out to be too much of a hassle. So the wiki actually only got updated once a week. And that's not good for transparency of course.

So this time around we went searching for a simple tool that would lower the threshold of updating the burndown chart on our wiki. We searched for an extension to MediaWiki that allows you to create a chart by just entering the numbers in your wiki text. That turned out to be quite a challenge. There are many charting and drawing extensions for MediaWiki, but they either didn't do what I wanted or we couldn't get them to work on our wiki.

In the end I just gave up and wrote a simple web page that -when fed with the right parameters- will return a PNG image of the burndown chart. You call the page like this:

  • burndown.jsp?days=1,2,3,6,7,8,9,10,13,14&work=200,170,165,150,125,95
And the page will return the following image:
So the days parameter indicates the day numbers shown on the bottom. I entered all of them for the entire sprint right away. The work parameter is the work remaining. I just entered the values that I know, which is why the green line stops halfway through.

The generated chart is really simple and not very pretty. But it is very easy to keep up to date and that's what counts most. I just add the remaining hours at the end of the URL every morning... and that's it.

Although I consider this generator a stop gap solution until I find something better, I imagine it might also be useful to other budding Scrum masters. For that reason I've put the page online for public use at Just click the link and you'll get some usage examples.

Let me know if this generator is useful to you in the comments section. Also let me know if there's something wrong with it and I'll do my best to fix it.

Update (January 1st, 2010): in my company we've created a custom version of this same tool and used that in many projects over the last few years. This public burndown generator has drawn over 60.000 charts in 2009 alone, so apparently we're not the only ones who use burndown charts. That's why I've now updated the tool with the best features that we've added over time at my company. Check the latest version on for all the features and let me know what you think of them.

Sunday, August 19, 2007

Scrum: utilization vs. velocity

At work we're recently started using Scrum for running some projects. As expected we need to slowly learn the lessons. One of the things we're been having a lot of discussion on recently is the meaning of the focus factor. Let me begin by explaining what a focus factor is, at least in my company.

To determine how much work you can do in a sprint, you need to estimate the top stories. We estimate these stories in "ideal man days" using planning poker. This means that each developer answers the question: if we lock you into a room each day without any distractions, after how many days would you have this story finished?

After these estimates we determine people's availability for the project. After all, they might also be assigned to other projects, if only for part of their time. Even people that have no other projects, tend to have other activities. Like answering questions from customer support or consultants, department meetings, company wide meetings, job interviews with candidates or just playing a game of fusball, table tennis or bowling on the Wii. So basically nobody is available to a project 100% of the time. At most it's 80% - 90% and on overage it seems to be about 60% - 70%.

So the first stab at determining how much work someone can complete is:

  • available hours = contract hours * availability
But when you're working on the project, you're not going to always be contributing towards the goals that you've picked up. Within Scrum there is the daily Scrum meeting. It lasts no more than 15 minutes, but those are minutes that nobody in the team is working towards the goal. And after the meeting a few team members always stick around to discuss some problem further. Such time is very well spent, but it probably wasn't included in the original estimate. So it doesn't bring the "remaining hours" down very much. I see all this meeting, discussion, coaching and tutoring as necessary work. But work that doesn't bring the team much closer to the goal of the sprint. I used to call this overhead, but that sounded like we were generating waste. So in lieu of the agile world I switched to using the term focus factor. So now we have:
  • velocity = contract hours * availability * focus factor
So the speed at which we get things done (velocity) is the time we're working minus the time we loose to non-project work minus the time we loose on work that doesn't immediately get us closer to the goal. In the past I probably would have included a few more factors in there, but in an agile world this is already accurate enough to get a decent indication of how long it will take us to get something done.

If there's one thing I've learned from the agile movement and Scrum it's to focus on "when will it be done" instead of "how much time will it take". So to focus on velocity instead of utilization.

Utilization is the territory of classic project management. It's trying to make sure that every hour of every employee is fully accounted for. So if they're programming, they should have a time-writing slot for programming; if they're meeting, there's a slot for meeting; if they're reviewing designs, there's a slot for that and if they're drinking coffee or playing the Wii... you get the picture. Of course there's no project manager that wants all that level of detail. But in general they are focused on what you're spending your time on.

Agile thinkers see this really differently. They say: it doesn't really matter how much time you spend, what matters is when it is done. This sounds contradictory so let's see if a small example can make it clearer what I'm trying to say.

If I tell my boss that some feature he wants will be done at the end of next week, he is interested in only one thing: that it is done next week. If we get it done on time, he doesn't care whether I spent two hours per day on it or whether it was twelve hours per day. I care about it of course, because I don't want to work late every night. And there's also a limit to the amount of gaming I like to do during a day, so two hours per day will leave me bored quickly. But to my boss, all that matters is when I deliver, not how much effort it took.

This is why the focus for Scrum projects is on velocity and not on utilization. So in Scrum you want to know how many hours you still need to spend on a job, not how many you've already spent on it. A classic project manager might be really proud that you worked late all week and clocked in 50+ hours. An agile project manager will note that you reduced the "hours remaining" by 10 hours and nothing more. If you're looking for compliments on all your hard work, then Scrum might not be for you.

Learn more:

Saturday, August 11, 2007

Will wireless work?

Friends often call me a geek. They mean no offense, so I try to take none. As Chris Pirillo once put it: "geek used to be a four letter word, now it's a six figure one". Well... that last part isn't exactly true for me, but that's probably only so because I get paid in euros instead of dollars.

Part of what makes me a geek is the fact that I tend to be an early adopter of new technologies. I got my first always-on internet connection in 1996 paying somewhere around 40 euros for a speed that never seemed to top 1.5 kbps. Yes, that's kpbs for kilobits per second - so about 40 times slower than an analog modem. But it was always on... so I was one of those people that knew they had email a few seconds after the other party had sent it.

I bought an XDA in 2001, which was the first touch-screen phone/pda with an internet connection. It was what you'd call an iPhone these days, although it had to do with a lot less marketing. So for me: six years have brought us better marketing and a multi-touch screen. Still... I'l probably buy an iPhone when they're actually available here. Not because I need it. Just because I'm an early adopter.

As an early adopter you of course run the risk of buying things that will never catch on. Or becoming the involuntary beta tester of a device, which means the technology is not yet ready for prime time. One area where the latter happened to me is with wireless networking.
I bought my first wireless access point and card somewhere in 2001. It wasn't completely new back then, but it hadn't been adopted by the masses yet. So usability and interoperability left something to be desired. USB wasn't as ubiquitous as it is now, so for a desktop PC I had to use a PCI to PCMCIA (now called PC-card and almost extinct) adapter. But hey... it worked... at times. But about half of the time it didn't work and I had to roll out a UTP cable again. I've tried to get a reliable wireless network over the years, but the devices either didn't work reliably or just broke down within a few months of service.

Somewhere in 2004 I just gave up on it and restored the cables to their full and permanent glory. So when whole tribes, states and even countries started using wireless networking, my house is completely wired. It's been like that for years now; first with really long UTP cables running down the hallways. They might not be pretty, but at least they work most of the time.

Two years ago I started using ethernet-over-powerline adapters, which use he powerline network in my house serves as a network. These adapters turned out to be as reliable as using direct UTP cables. So in my study I connect the ADSL modem/router to the powerline through one of these adapters. And in other rooms I connect computers to the powerline through another adapter. And it just works.

The adapters are ridiculously expensive and not very rugged, but they do give me the true plug-and-play experience that I never got with wifi. And even though having blue adapters in many wall sockets is not very pretty, it's a lot better than all those colorful UTP cables lining the floor. So -although expensive- I was pretty happy with it. Most people may prefer wifi, I've been sticking with ethernet-over-powerline.

A few weeks ago I saw a new device from Devolo: a wireless extender. So you plug this adapter into a socket and not only can you plug in an UTP cable, but it also provides wireless networking. So once again I couldn't resist and ordered one. If the whole world is using wireless without problems, I can't stay behind - can I?

Friday, August 3, 2007

Both, either or any

I recently was adding functionality to a part of our product that was full of lines like this:

  • lBool_vert_in = this.IsBoathBitsSet(iArrAllow[key], iArrDeny[key],
  • top.mTDSDefines_CheckInAction);
At first I was just annoyed by the obvious typo in there. I'm sure a boath is something (maybe a very expensive boat) but it has no place in our code. Making a typing error is not strange, it's actually quite normal. But not correcting it when you're copy/pasting it at least a few dozen times is a kind of laziness that I don't like very much.

Later I also needed to know what the function does. At first I thought the name was actually pretty self-describing. But I couldn't explain the behavior I was seeing in a part of the code that invoked this function.
  • this.IsBoathBitsSet = function(iBit1Value, iBit2Value, iDefineType)
  • {
  • return (
  • (
  • (iBit1Value & iDefineType)||
  • (iBit2Value & iDefineType)
  • ) == iDefineType )
  • }
Now that strikes me as odd... the function name suggests that both bits need to be set. This would normally translate into an && and not into an || like in this code. So instead of just a simple typo, this function name is actually plain wrong. And it also immediately explained the behavior I was getting.

I was thinking of renaming the function. But what shuld I rename it to? At first I was thinking IsEitherBitSet, since it returns true if either bit it set. But that is also not entirely correct. Since it also returns true if both bits are set.

So maybe it should be called IsAnyBitSet. What do you think? How do you translate boolean operators into English?