Decsribing compound resources/hierarchical collections

How can I describe hierarchical collections, using Arbil? Consulting this FAQ item:, I tried to add cmdi files as resources, but was not allowed to. Advice, please.

Sorry for the late reply. I must have overlooked this.

The easiest way to create a CMDI hierarchy in Arbil is to create both the parent and the child CMDI separately in Arbil and then dragging the child into the parent.