A year ago I was the architect of a small project (Project A) building a Client / Server application, based on Eclipse SWT/JFace/RCP, Websphere, Oracle, JMS and an Object Relation Mapping (ORM) tool, Hibernate. We were 3.5 developers on average, and we finished in 7 months. We used Feature Driven Development (FDD, similar to eXtreme Programming) as its implementation methodology.
This year I worked as a lead developer on a much larger project (Project B), which I joined in its second half. The project as a whole had nearly 50 people on it at times, although our part was again an Eclipse SWT/JFace/RCP Client using a Websphere Server with Oracle and a different ORM tool, Toplink. We were 5 developers on average, finishing in 9 months. Here a kind of waterfall based methodology was used.
In my spare time, I work on a tiny project, BookStore. Again an Eclipse SWT/JFace/RCP Client but not using Websphere, and instead of Oracle it uses MySQL but also with Hibernate. Its developed by just me. I do however track time spent on implementation, as well as metrics. The methodology used here is an extremely Agile one, where the documents are in the code (unless its really major, then it gets its own document), priority is given to bug fixing, then feature development, then product improvement. The aim is to be able to release a stable version at any time so that bugs can be fixed super quick. The product auto-updates from the web, to enable this.
Last week was interesting when we measured some generic metrics for Project B. I did this as part of every release for Project A and BookStore, since I find these things interesting.
A summary of the results are as follows:
|Metric Name||Project A||Project B||BookStore|
|Total Lines of Code||48,000||46,000||24,000|
|Approximate Man Months||24||38||2|
|Depth of Inheritance Tree||2.7||1.9||2.8|
|Number of Classes||416||223||247|
|Number of Methods per Class||7.3||10.3||6.3|
What does all this mean?
The Total Lines of Code, Approximate Man Months and Productivity (Thousand Lines of code per month) all help to give a feeling of the size and complexity of the projects. Interesting would be to count the number of features, but that is sooo subjective, there is no point in even starting it. What is interesting, is that Projects A and B produced a similar amount of code, and from my experience of both of them, they were of roughly the same complexity. However the shear size of Project B, in terms of other activities and applications (for example a web application, integration with systems of other companies, etc.) means that the number of lines of communication are greatly increased. Getting information in order to implement something was much much harder. So that is a good explanation of why the project was so much less productive. Comparing Project A to BookStore is also interesting. Although BookStore was half the size, it was hugely more productive. Even if you scale its figures up and say that to get it to the same number of lines of code it takes 4 times longer, the productivity index is 6.0, three times higher than for Project A. The reasons are again simple, in that its a single developer project. There are almost no lines of communication (except with Beta Testers and Customers), so no time is wasted hunting for the right answers. I think it is in Peopleware by Tom DeMarco and Timothy Lister, where they talk about 50% of your time being spent on non-software related activities, like phone calls and email. Well for BookStore probably only 10% of time was spent on such activities, precisely because the number of lines of communications was so low. Sadly controlling the number of lines of communication on a project might be impossible to reduce below a certain size, because of stake holders in the project. If you integrate with external systems and other projects, you have no way to reduce those communications, beyond strategies like having one point of contact per technical area. But if that one point of contact needs time themselves to determine information, it might not help. Simply put, the communication network is hard to control, especially as a techie / non-senior manager.
The other metrics, such as Depth of Inheritance Tree, Abstractness, Number of Classes and Number of Methods per Class tell a different story. These relate much more to the design of the software, something that can be controlled by the technical team. My aim when designing software (which incedentally does not need to happen before you code, it can happen during coding, by means of agile refactoring) is NOT to have the perfect design... But I do believe in using design patterns and inheritance when its useful. I might add it by refactoring, if I am unsure it will be of use at the start (see my article on DT, EMV and NPR revisited). Anyway, the results above show that when I am fully in charge (BookStore) a clean design results. When I am mostly in charge (Project A) a clean design results. When I have only a little influence, the design is less clean (not only shown by figures, but also by code reviews conducted by myself). So what? Well that might have something to do with the productivity. But it also has a lot to do with maintainance and future releases of the software. For Project B, an entire new team is taking over and it is unlikely to have major changes for 6 months after delivery, so a lot of knowledge will get lost. A clean design would be useful in this case, since ramp up time for new team members would be smaller. One day I might sell BookStore to a company who wants to take it further, and they would want a clean design to do that.
There are of course other factors at play here. Project B had a user interface that had requirements to be fully useable without a mouse. Implementing radio buttons within a table which are selectable with the space bar are rock hard to build, compared to just using an SWT or Swing radio button. And all that effort does not really show up as some great feature!
BookStore on the other hand shyed away from anything difficult. It was built under the paradigm "Keep it simple, stupid". This was precisely because I know that complex requirements that give little usability are dangerous to productivity. Normally I recommend my clients to steer clear, but Project B was so big, and so politically charged, with a customer who didn't seem to really care about costs, that it was not possible to change the requirements in order to aid productivity.
I also like to think that agile projects, like Project A and BookStore, are more productive because they are agile. Fixing bugs as you find them, developer testing, quick releases to help testers retest bugs, etc. are all good things in modern software development. Refactoring as you go to ensure you have the ideal depth of design means that overall you keep your costs down - you don't spend unnecessarily on design at the start, but you do spend on it when required to keep the code maintainable for the long term.
For me, lessons learned from these results are summed up as follows. If you want to keep productivity high, and make the code maintainable in the long term, then:
- develop using an agile method,
- control requirements changes, to keep costs due to change at a minimum,
- refactor continuously to keep a clean design,
- throw out expensive requirements that give little or no return on investment,
- reduce lines of communication to a minumum - one point of contact per technical area
- employ decision makers - people who can make good decisions reduce the need for changes later and messing about now
OK, that last point seems to have come out of nowhere, but its still valid :-) And all the others are nothing new if you have read a book about agile development. But the results from these three projects seem to back up what the literature says.
Incidentally, the metrics shown here were measured using an Ecplipse Plugin available from http://metrics.sourceforge.net. That site contains further information about these metrics and their meanings.