A relationship node identifies a data relationship between two different object instances. A relationship node always has the same format. An example of a relationship node follows:
<IObject UID="e6f7de0c-fae2-4bf6-8f0e-783574fa465a" />
The root node of a relationship node is always a "Rel" node. The root node contains two child interface nodes, IObject and IRel.
The IObject node, just like with an object node, specifies the globally unique identifier for the relationship instance.
The IRel node specifies three pieces of information:
DefUID – the UID of the relationship type
UID1 – the UID of the object on one side of the relationship
UID2 – the UID of the object on the other side of the relationship