Background:
1. There might be an exiting external inventory system, operating the PNF instances, and exporting the PNF instances to ONAP`s AAI in "inventoried status".
These need to be supported.
2. It might happen, that a Service Instance using a PNF instance would be deleted, and the PNF instance will be kept in AAI, in e.g. "inventoried" status. We`d like to pick such an instance up for macro service instantiation later on.

Goal:
Make it possible to use an existing (in ONAP`s AAI) PNF instance in a macro service orchestration. The eligible PNF instance need to fulfill a few requirements, e.g. not in "active" state, not attached to an existing (active) Service Instance.