ACM Transactions on Database Systems

We propose an object-oriented data model that generalizes the relational, hierarchical, and network models. A database scheme in this model is a directed graph, whose leaves represent data and whose internal nodes represent connections among the data. ...

The nested relational model extends the flat relational model by relaxing the first normal form assumption in order to allow the modeling of complex objects. Much of the previous work on the nested relational model has concentrated on defining the data ...

The semantics of objects and transactions in database systems are investigated. User-defined predicates called consistency assertions are used to specify user programs. Three new correctness criteria are proposed. The first correctness criterion ...

Suppose a database schema D is extended to D¯ by adding new relation schemas, and states for D are extended to states for D¯ by applying joins and projections to existing relations. It is shown that certain desirable properties that D¯ has with respect ...

Several graph-based algorithms have been proposed in the literature to compute the transitive closure of a directed graph. We develop two new algorithms (Basic_TC and Gobal_DFTC) and compare the performance of their implementations in a disk-based ...