A simplied universal relation assumption and its properties
ACM Transactions on Database Systems (TODS)
Computational problems related to the design of normal form relational schemas
ACM Transactions on Database Systems (TODS)
The theory of joins in relational databases
ACM Transactions on Database Systems (TODS)
Testing implications of data dependencies
ACM Transactions on Database Systems (TODS)
Synthesizing third normal form relations from functional dependencies
ACM Transactions on Database Systems (TODS)
On the Complexity of Testing Implications of Functional and Join Dependencies
Journal of the ACM (JACM)
On the Desirability of Acyclic Database Schemes
Journal of the ACM (JACM)
Graph Algorithms for Functional Dependency Manipulation
Journal of the ACM (JACM)
A relational model of data for large shared data banks
Communications of the ACM
Principles of Database Systems
Principles of Database Systems
Properties of database schemata with functional dependencies
PODS '84 Proceedings of the 3rd ACM SIGACT-SIGMOD symposium on Principles of database systems
On equivalences of database schemes
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
Transforming cyclic schemas into trees
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
Graphs and Hypergraphs
Alpha-acyclic decompositions of relational database schemes
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
The complexity of acyclic conjunctive queries
Journal of the ACM (JACM)
Equivalence and Mapping of Database Schemes
VLDB '84 Proceedings of the 10th International Conference on Very Large Data Bases
Weighted hypertree decompositions and optimal query plans
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Query answering exploiting structural properties
ACM SIGMOD Record
Uniform Constraint Satisfaction Problems and Database Theory
Complexity of Constraints
Generalized hypertree decompositions: NP-hardness and tractable variants
Journal of the ACM (JACM)
Constructing the Bayesian network structure from dependencies implied in multiple relational schemas
Expert Systems with Applications: An International Journal
Derivation digraphs for dependencies in ordinal and similarity-based data
Information Sciences: an International Journal
Hi-index | 0.01 |
A hypergraph formalism is introduced to represent database schemata. In particular, a database schema B, described by one full join dependency and a set of functional dependencies, is represented by a (database) hypergraph H, containing both undirected and directed hyperedges. Undirected hyperedges correspond to the relations in the join dependency, and directed hyperedges correspond to the functional dependencies. In addition, two classes of database hypergraphs are defined: e-acyclic hypergraphs and e-independent hypergraphs. A hypergraph is e-acyclic if it is equivalent to some acyclic hypergraph; it is e-independent if it is equivalent to some independent (i.e., cover-embedding) hypergraph. Furthermore, the closure of a database hypergraph is defined as the extension of the transitive closure of a graph. By using a lower bound and an upper bound of the hypergraph closure (called L-closure and U-closure, respectively), it is proved that two e-acyclic (e-independent) hypergraphs are equivalent if and only if they have the same closure. Moreover, a hypergraph is e-acyclic (e-independent) if and only if its closure is acyclic (independent) and, in most cases, such a recognition can be done in polynomial time. Finally, it is shown how to use the database hypergraph closure to solve some database design problems.