In YAGO (as in RDF), each fact consists of a subject, a predicate, and an object. Every fact can have a fact id. This allows facts to talk about other facts. The fact id is simply computed as a hash from the subject, predicate, and object of the fact. An example fact is

<id_abcd> <Elvis_Presley>  <marriedTo>  <Priscilla_Presley>

Yago has some neat stuff.