For other constituents I've seen birth/death dates. So if a particular constituent has no birth date (and separately no death date), skip those nodes and the incoming relation.
This particular constituent was one of the zombies, and no longer exists. I anyway modified the model to remove nodes where there are no birth/death dates.
http://data.americanartcollaborative.org/page/puam/constituent/6388/birth http://data.americanartcollaborative.org/page/puam/constituent/6388/death have no data at all.
For other constituents I've seen birth/death dates. So if a particular constituent has no birth date (and separately no death date), skip those nodes and the incoming relation.