<element name="sdf" required="1">
<description>SDFormat base element that can include one model, actor, light, or worlds. A user of multiple worlds could run parallel instances of simulation, or offer selection of a world at runtime.</description>
<attribute name="version" type="string" default="1.9" required="1">
<description>
Version number of the SDFormat specification, consisting of major
and minor versions delimited by a `.` character.
A major version bump is required if older versions cannot be
automatically converted to this version.
A minor version bump is required when there are breaking changes that
can be handled by the automatic conversion functionality encoded in the
`*.convert` files.
</description>
</attribute>
<include filename="world.sdf" required="*"/>
<include filename="model.sdf" required="0"/>
<include filename="actor.sdf" required="0"/>
<include filename="light.sdf" required="0"/>
</element> <!-- End SDF -->