When specifying the attribute end_range for an integer generator, if start_range is missing then DG throws a NullPointerException. If this is expected behaviour (i.e. start_range and end_range must be specified together) then it should be noted in the documentation since it lists both of these fields as optional. Although the documentation says that if the start_range isn't specified it will be set as default to 1, so start_range shouldn't be required in order to use end_range based on this.
This will cause DG to throw the exception if it's in the xml:
<attr name="name" value="director_id"/>
<attr name="type" value="INTEGER"/>
<attr name="constraint" value="NOT NULL"/>
<attr name="type" value="integer"/>
<attr name="seq" value="false"/>
<attr name="end_range" value="7000"/>