It’s obvious that a woman can create a baby in 9 months, but 9 women cannot create a baby in 1 month. This is the idea which The Mythical Man-Month wants to explain. If a job can be done by 5 men in 1 month, it’s said that this job requires 5 man-months. So applying simple arithmetic, would this project be completed in half the time if 10 men work on it? In the software development world, this thought is an outright fallacy. It’s not possible to multiply people by hours. The cost of a project is proportional to the man/months, but the progress is not.

Sometimes, assigning more people to a project to speed up the development is not the best idea, due to the time required to explain, learn, understand, mets, … about the project. Also we can find non-divisible tasks, so only one person can to do it. If we want to reduce the time, the way to do this is not by adding developers but discarding functionalities not implemented yet. For example, in DSDM we have the time and the resources fixed and the functionalities are variable (they depends on the fixed stuff).

The Mythical Man-Month is a chapter of a book called The Mythical Man-Month: Essays on Software Engineering written by Fred Brooks. This book was written 32 years ago, and it’s been one of the most transcendental books about software project management. It was republished as an anniversary edition in 1995 with the essay No Silver Bullet, where the author maintains the idea that there isn’t single development, in either technology or in management technique, that by itself promises even one order-of-magnitude improvement in productivity, in reliability or in simplicity. The main question is: Is it possible to develop without developers?

Continuous integration is a software engineering practice, which helps to integrate changes frequently in a project. It speeds up the delivery of software by decreasing integration times. It’s very important when the project is being developed by more than one person. CruiseControl is a free CI server and probably the most used. Xinc (Xinc Is Not Cruisecontrol) is an alternative free CI server made specially for PHP. The Xinc development is led by Arno Schneider, a german developer currently living in Barcelona. Arno made a wonderful presentation at the Barcelona PHP Conference celebrated last month:

We can install Xinc easily with PEAR.

sudo pear channel-discover pear.xinc.eu
sudo pear install --alldeps xinc/Xinc
sudo pear run-scripts xinc/Xinc

When we run the scripts, we can configure some parameters like:

 1. Directory to keep the Xinc config files: /etc/xinc
 2. Directory to keep the Xinc Projects and Status information: /var/xinc
 3. Directory to keep the Xinc log files: /var/log
 4. Directory to install the Xinc start/stop daemon: /etc/init.d
 5. Do you want to install the SimpleProject example: yes
 6. Directory to install the Xinc web-application: /var/www/xinc
 7. IP of Xinc web-application: 127.0.0.1
 8. Port of Xinc web-application: 8080

Once the installation is complete, we need to include /etc/xinc/www.conf in our apache virtual hosts. We also have to have mod-rewrite enabled.

This tip probably seems a bit stupid, but I have always found very useful. If we want to replace a string in a file with another string, we can do it easily using Perl:

perl -p -i -e 's|old_string|new_string|' file.xml

Of course, if we need to apply it to several files we can use a wildcard character.

The beta version of the latest Ubuntu, Hardy Heron 8.04, has been released. The official release will be on April 24th 2008.

Link | Ubuntu releases

Paolo Maldini, as know as Il Capitano said goodbye to the top flight of football after a thrilling match against Arsenal FC. Maldini has been one of the best defenders in the world, and after 24 seasons playing at AC Milan, Maldini will retire from the fields. The rossonero team has said that the number three that Paolo Maldini has used since his debut will not be assigned to any player ever again after his retirement, except his children Christian and Daniel, if someday they would play in the first team.

One use of the lower-case Greek letter λ is a branch of mathematical logic called Lambda Calculus. It’s a formal system designed to research function definition, function application and recursion. Throughout the years, λ has been seen on many logos related with the functional programming. For example, the MIT Scheme’s logo represents a recursive shield with lambda:

We can see lambda on the functional programming language Haskell’s logo. Apart from lambda, we can see five other mathematical symbols, representing the Haskell’s functionality. These are their respective meanings:

-The right arrow (→): Transformation
-The universal quantification (∀): For all
-The double angle (≫): Free from disorder
-The double right arrow (⇒): Generality
-The double colon (::): Exactitude

A scheme-to-C compiler called Chicken has a logo that represents a lambda inside a hen silhouette.

CL-HTTP (Common Lisp Hypermedia Server) has a lambda symbol on its logo too.

More information | Xahlee