Distinguishing Component Parts of a <Model>
Decomposing a <Model> into component models allows the data provider to
- reuse component parts
- distinguish moving parts
Component vs. root model
- component model - can be instanced only in the scope of another <Model>
- root model - can be instanced only in the scope of an <Environment Root> instance
- both - can be instanced in the scope of either a <Model> or an <Environment Root>
One catch: Each <Model> has its very own spatial reference frame. How do we resolve this?