6NF???!? Sounds like a challenging class and not just because of a possible language barrier (for me). Following the "6NF" trail led me to this page: http://www.dbdebunk.com/books.html ...which links to a book about temporal data in a relational model. Might be worth a look, considering the source. GL! Rich > Here's an interesting commentary on it from the big O website: > > > > http://www.oracle.com/global/nl/education/specials/sp269.htm -- //www.freelists.org/webpage/oracle-l