This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
Abder-Rahman, it would help is you were a little more specific about what software you are working with. I will assume you are asking a question about the Ant build.xml file. In that case I will forward you to the documentation: http://ant.apache.org/manual/CoreTypes/fileset.html
If after reading that you have some specific questions about it, then feel free to ask.