About: http://webisa.webdatacommons.org/245310380

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	As you said yourself, there is a limit to the number of aliens per UFO, and there is a limited number of alien types and weapons, so eventually, they will stop advancing.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com