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 :)
B. Pereira Nunes, R. Kawase, S. Dietze, D. Taibi, M. Casanova, and W. Nejdl. Proceedings of the Web of Linked Entities Workshop in conjuction with the 11th International Semantic Web Conference, volume 906 of CEUR-WS.org, page 45--57. (November 2012)
J. Yang, and J. Leskovec. Proceedings of the Sixth ACM International Conference on Web Search and Data Mining, page 587--596. New York, NY, USA, ACM, (2013)