Part composition follow ups

[aothms]

I have one more scenario to consider. Perhaps it already was (and if so, if there are any documented discussions it would be great to get a reference). Should a site be able to compose a facility?
Ie if I have a road facility, it might be composed of multiple sites. If this isn't permitted, then the class IfcSpace would be the likely candidate to be used in a containment hierarchy. An alternative implementation might be to have sites in their own hierarchy and have elements referenced to the site. At least one authoring application authors multiple sites and the root element as a facility (ie ifcroad, or Ifcrail) would be a logical choice to me.

Originally posted by @jmirtsch in #176 (comment)