<element name="world" required="*">
<attribute name="name" type="string" default="__default__" required="1"/>
<include filename="gui.sdf" required="0"/>
<include filename="physics.sdf" required="1"/>
<include filename="scene.sdf" required="1"/>
<include filename="light.sdf" required="*"/>
<include filename="model.sdf" required="*"/>
<include filename="actor.sdf" required="*"/>
<include filename="plugin.sdf" required="*"/>
<include filename="joint.sdf" required="*"/>
<include filename="road.sdf" required="*"/>
<include filename="state.sdf" required="*"/>
</element> <!-- End World -->