# A simplied universal relation assumption and its properties

@article{Fagin1982ASU, title={A simplied universal relation assumption and its properties}, author={Ronald Fagin and Alberto O. Mendelzon and Jeffrey D. Ullman}, journal={ACM Trans. Database Syst.}, year={1982}, volume={7}, pages={343-360} }

One problem concerning the universal relation assumption is the inability of known methods to obtain a database scheme design in the general case, where the real-world constraints are given by a set of dependencies that includes embedded multivalued dependencies. We propose a simpler method of describing the real world, where constraints are given by functional dependencies and a single join dependency. The relationship between this method of defining the real world and the classical methods is… Expand

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#### References

SHOWING 1-10 OF 42 REFERENCES

On the menbership problem for functional and multivalued dependencies in relational databases

- Computer Science
- TODS
- 1980

The problem of whether a given dependency in a database relation can be derived from a given set of dependencies is investigated. We show that the problem can be decided in polynomial time when the… Expand

Multivalued dependencies and a new normal form for relational databases

- Computer Science
- TODS
- 1977

It is shown that every relation schema can be decomposed into a family of relation schemata in fourth normal form without loss of information (that is, the original relation can be obtained from the new relations by taking joins). Expand

Equivalence of relational database schemes

- Computer Science
- STOC
- 1979

It is argued that this question reduces to the equivalence of the sets of fixed points of the project-join mappings associated with the two database schemes in question, and the “update sets” approach to database design is introduced. Expand

Equivalence of Relational Database Schemes

- Mathematics, Computer Science
- SIAM J. Comput.
- 1981

It is argued that this question reduces to the equivalence of the sets of fixed points of the project-join mappings associated with the two database schemes in question, and the “update sets” approach to database design is introduced. Expand

A Sophisticate's Introduction to Database Normalization Theory

- Computer Science
- VLDB
- 1978

This paper is intended to serve the two-fold purpose of introducing the main issues and theorems of formal database semantics to the uninitiated, and to clarify the terminology of the field. Expand

A complete axiomatization for functional and multivalued dependencies in database relations

- Computer Science, Physics
- SIGMOD '77
- 1977

The main result of the paper is that the rules presented are complete for the family of functional and multivalued dependencies. Expand

Generalized Mutual Dependencies And The Decomposition Of Database Relations

- Computer Science
- Fifth International Conference on Very Large Data Bases, 1979.
- 1979

This work shows that a generalized mutual dependency, together with a set of multivalued dependencies, provide a necessary and sufficient condition for a relation to be decomposable in the general case. Expand

Synthesizing third normal form relations from functional dependencies

- Computer Science
- TODS
- 1976

An effective procedure for performing a relational scheme synthesis is presented and the schema that results from this procedure is proved to be in Codd's third normal form and to contain the fewest possible number of relations. Expand

Real-world MVD's

- Computer Science
- SIGMOD '81
- 1981

This paper investigates how much complexity is actually needed in real-world situations by showing that every "natural" set of mvd's must belong to a class of m DVD's called conflict-free, and it is shown that adding semantic concepts amounts to making the set ofmvd's conflict- free. Expand

Testing implications of data dependencies

- Computer Science
- SIGMOD '79
- 1979

The chase can be used to test equivalence of database schemes and as part of the test of whether the relation schemes in a database scheme are independent components. Expand