A normal form for relational databases that is based on domains and keys
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)
Variations on the Common Subexpression Problem
Journal of the ACM (JACM)
Testing satisfaction of functional dependencies
Journal of the ACM (JACM)
Principles of Database Systems
Principles of Database Systems
Data Models
Synthesizing independent database schemas
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
Improving semantic specification in a relational database
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
A formal treatment of imperfect information in database management
A formal treatment of imperfect information in database management
Satisfying database states
Database states and their tableaux
ACM Transactions on Database Systems (TODS)
PODS '83 Proceedings of the 2nd ACM SIGACT-SIGMOD symposium on Principles of database systems
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We discuss the objectives of including functional dependencies in the definition of a relational database. We find two distinct objectives. The appearance of a dependency in the definition of a database indicates that the states of the database are to encode a function. A method based on the chase of calculating the function encoded by a particular state is given and compared to methods utilizing derivations of the dependency. A test for deciding whether the states of a schema may encode a nonempty function is presented as is a characterization of the class of schemas which are capable of encoding nonempty functions for all the dependencies in the definition. This class is the class of dependency preserving schemas as defined by Beeri et al. and is strictly larger than the class presented by Bernstein.The second objective of including a functional dependency in the definition of a database is that the dependency be capable of constraining the states of the database; that is, capable of uncovering input errors made by the users. We show that this capability is weaker than the first objective; thus, even dependencies whose functions are everywhere empty may still act as constraints. Bounds on the requirements for a dependency to act as a constraint are derived.These results are founded on the notion of a weak instance for a database state, which replaces the universal relation instance assumption and is both intuitively and computationally more nearly acceptable.