An agent is something or someone that can act on its own and produce changes in the world. There is more to agenthood than that, but for this ontology that is all that matters.
(Subclass-Partition Biblio-Thing
(Setof Agent
Timepoint
Document
Reference
Conference))
(=> (Agent ?X) (Value-Cardinality ?X Agent.Name 1))
(=> (Agent.Name $X $Y) (Agent $X))