Better defaults
When an argument is not given, it's better not to set it at all.
For example jpseditor
outputs this
<source id="1" frequency="0" N_create="10" percent="0" rate="0" time_min="0" time_max="0"
agents_max="100" group_id="5" caption="Source1" greedy="false" time="0" startX="0" startY="0" x_min="4.85"
x_max="5.97" y_min="25.14" y_max="26.1"/>
Better would be
<source id="1" frequency="0" N_create="10"
agents_max="100" group_id="5" caption="Source1" greedy="false" x_min="4.85"
x_max="5.97" y_min="25.14" y_max="26.1"/>