Non first normal form relations to represent hierarchically organized data

Several investigators have stressed that the first normal form (1NF) condition [Co] is not convenient for handling a variety of database applications CM,K,JS,SPl. The first purpose of this paper is to present a database model, namely, the Verso model, where data is organized in non 1NF relations. The values for some attributes in 8 Verso instance are atomic whereas the values for other attributes are simpler Verso instances. As we shall see, this recursive definition of the data structure induces a hierarchical organization of the data. Several models have ttiied to capture the notion of hierarchical data organization [IMS,HY]. The advantage of our approach is that, by using relation as underlying structure, we are able to preserve some of the positive features of the relational model, for instance, a simple algebraic query language.