Database Systems (TODS)


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ACM Transactions on Database Systems (TODS), Volume 18 Issue 3, Sept. 1993

The logical data model
Gabriel M. Kuper, Moshe Y. Vardi
Pages: 379-413
DOI: 10.1145/155271.155274
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...

Semantics for null extended nested relations
Mark Levene, George Loizou
Pages: 414-459
DOI: 10.1145/155271.155275
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...

Consistency and orderability: semantics-based correctness criteria for databases
Divyakant Agrawal, Amr El Abbadi, Ambuj K. Singh
Pages: 460-486
DOI: 10.1145/155271.155276
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...

Solving queries by tree projections
Yehoshua Sagiv, Oded Shmueli
Pages: 487-511
DOI: 10.1145/155271.155277
Suppose a database schema D is extended to by adding new relation schemas, and states for D are extended to states for by applying joins and projections to existing relations....

Transitive closure algorithms based on graph traversal
Yannis Ioannidis, Raghu Ramakrishnan, Linda Winger
Pages: 512-576
DOI: 10.1145/155271.155273
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...