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 :)
This is a repository of databases, domain theories and data generators that are used by the machine learning community for the empirical analysis of machine learning algorithms.
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S. Simoff. Proceedings of the MDKM/KDD2000 Workshop on
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A. Arasu, and H. Garcia-Molina. Proceedings of the 2003 ACM SIGMOD International Conference on Management of Data, San Diego, California, USA, June 9-12, 2003, page 337-348. ACM, (2003)