On the sequential nature of unification
Journal of Logic Programming
On compiling queries in recursive first-order databases
Journal of the ACM (JACM)
Logic programming and databases
Proceedings from the first international workshop on Expert database systems
Implementation of logiclal query languages for databases (abstract only)
SIGMOD '85 Proceedings of the 1985 ACM SIGMOD international conference on Management of data
Database abstractions: aggregation and generalization
ACM Transactions on Database Systems (TODS)
A Proof Procedure Using Connection Graphs
Journal of the ACM (JACM)
Logic and Databases: A Deductive Approach
ACM Computing Surveys (CSUR)
Universality of data retrieval languages
POPL '79 Proceedings of the 6th ACM SIGACT-SIGPLAN symposium on Principles of programming languages
SIGMOD '83 Proceedings of the 1983 ACM SIGMOD international conference on Management of data
An implementation of GEM: supporting a semantic data model on a relational back-end.
SIGMOD '84 Proceedings of the 1984 ACM SIGMOD international conference on Management of data
An optimizing prolog front-end to a relational query system
SIGMOD '84 Proceedings of the 1984 ACM SIGMOD international conference on Management of data
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The Relational Data Model and Relational Calculus are extended with Unification and non-recursive Horn Clauses from Logic. The benefits gained include better versatility and a richer functionality for expressing complex Jack, deductive queries and rule-based infer- ences. Applications include semantic data models for Databases, frames for Knowledge-based systems, and Complex Objects for CAD. An Extended Relational Algebra (ERA) is introduced that has the same expres- sive power as the new Calculus. The algorithm given for translating from Calculus to ERA supplies a sound basis for the compilation of these Horn clauses, and their implementation using query optimization and other techniques currently used in database systems.