Revisiting the hierarchical data model

Much of the data we deal with every day is organized hierarchically: file s ystems, library classification schemes and yellow page categories are salie nt examples. Business data too, benefits from a hierarchical organization, and indeed the hierarchical data model was quite prevalent thirty years ago . Due to the recently increased importance of X.500/LDAP directories, which are hierarchical, and the prevalence of aggregation hierarchies in datacub es, there is now renewed interest in the hierarchical organization of data. In this paper, we develop a framework for a modern hierarchical data model , substantially improved from the original version by taking advantage of t he lessons learned in the relational database context. We argue that this n ew hierarchical data model has many benefits with respect to the ubiquitous flat relational data model.