See also OTrunk ID System

In otrunk you can store references to other objects.
For this example lets say you two OTClasses: OTHouse OTDoor

You want your OTHouse to have a reference to a OTDoor.

To do this you modify your OTHouse interface or resource schema like this:

  OTDoor getDoor();
  void setDoor(OTDoor door);

There are a few ways this can be represented as in the otml.

OTDoor with uuid id and attribute reference in OTHouse

<OTDoor id="7B26E396-7DE9-4B6D-AE21-F6296DF1B8B8"/>
<OTHouse door="7B26E396-7DE9-4B6D-AE21-F6296DF1B8B8"/>

OTDoor with uuid id and element reference in OTHouse

<OTDoor id="7B26E396-7DE9-4B6D-AE21-F6296DF1B8B8"/>
<OTHouse>
   <door>
      <object refid="7B26E396-7DE9-4B6D-AE21-F6296DF1B8B8"/>
   </door>
</OTHouse>

OTDoor with local_id and attribute reference in OTHouse

<OTDoor local_id="door_id"/>
<OTHouse door="${door_id}"/>

OTDoor with local_id and element reference in OTHouse

<OTDoor local_id="door_id"/>
<OTHouse>
   <door>
      <object refid="${door_id}"/>
   </door>
</OTHouse>