The CAD Document item and it's ability to be related to Parts, BOMs, changes, etc. is used by the CAD Connectors created for Aras Innovator for CAD file management. The behavior to understand the related CAD Parts/Subassemblies/Drawings from a CAD Assembly is part of the CAD Connectors themselves. If you do not have a CAD Connector that understands the CAD authoring tool's parent-child relationships, you are going to end up doing it manually as you described. What CAD tool are you using? Are you interested in a CAD Connector to help with CAD file management from within the authoring tool? See link for more detail:
www.aras.com/.../cad-integration
It is the behavior of the CAD Authoring tools that an update to a child part/assembly is a change to the parent. If you use the default revision scheme, this is how your scenario should work:
Assembly, Component 1 & Component 2 released at Rev A - relationship gets "locked" at this point, so that the Released Rev A of the Assembly will always know that is has Released Rev A of both components
Minor change is required for Component 2 that does not require changing the parent Assembly. If you do as follows:
- Do a New Revision on Component 2, Rev B, this puts it into a Preliminary state at Rev B
- Change Component 2 and Release it at Rev B
- Released Rev A of the Assembly still points to Rev A of Component 2
- The next time the Assembly is Revised, it will default to the latest revision of Component 2, i.e. Rev B.
If there is a desire to keep Assembly at Rev A while actually having been modified to use Component 2 Rev B, then you will need to change the default behavior so that the Relationship doesn't get "locked" on Assembly Rev A at Release, so yes, you need to change the Item Behavior to Float with No Life-Cycle Behavior.
Hope this helps!