A pre-relational databases datamodel. "Preceeded" by the relational model since the flexibility of this makes it hard to work with. Now re-invented in RDF :)
T. Eliassi-Rad, and T. Critchlow. SAC '05: Proceedings of the 2005 ACM symposium on Applied computing, page 511--518. New York, NY, USA, ACM Press, (2005)