ACM Transactions on Database Systems (TODS)
On the representation of infinite temporal data and queries (extended abstract)
PODS '91 Proceedings of the tenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Towards a theory of spatial database queries (extended abstract)
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Selected papers of the 9th annual ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Relational expressive power of constraint query languages
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Variable independence and aggregation closure
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Constraint databases: promising technology or just intellectual exercise?
ACM Computing Surveys (CSUR) - Special issue: position statements on strategic directions in computing research
An expressive language for linear spatial database queries
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The DEDALE system for complex spatial queries
SIGMOD '98 Proceedings of the 1998 ACM SIGMOD international conference on Management of data
Equivalence of Relational Algebra and Relational Calculus Query Languages Having Aggregate Functions
Journal of the ACM (JACM)
A relational model of data for large shared data banks
Communications of the ACM
An Extended Algebra for Constraint Databases
IEEE Transactions on Knowledge and Data Engineering
Constraint Programming and Database Query Languages
TACS '94 Proceedings of the International Conference on Theoretical Aspects of Computer Software
Linear vs Polynomial Constraints in Database Query Languages
PPCP '94 Proceedings of the Second International Workshop on Principles and Practice of Constraint Programming
On the Desirability and Limitations of Linear Spatial Database Models
SSD '95 Proceedings of the 4th International Symposium on Advances in Spatial Databases
Manipulating Spatial Data in Constraint Databases
SSD '97 Proceedings of the 5th International Symposium on Advances in Spatial Databases
Eucil, Tarski, and Engler Encompassed (Preliminary Report)
DBLP-6 Proceedings of the 6th International Workshop on Database Programming Languages
Learning in Constraint Databases
DS '99 Proceedings of the Second International Conference on Discovery Science
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Constraint databases use constraints to model and query data. In particular, constraints allow a finite representation of infinite sets of relational tuples (also called generalized tuples). The choice of different logical theories to express constraints inside relational languages leads to the definition of constraint languages with different expressive power. Practical constraint database languages typically use linear constraints. This choice allows the use of effcient algorithms but, at the same time, some useful queries, needed by the considered application, may not be represented inside the resulting languages (for example, the convex hull cannot be computed [19]). These additional queries can only be modeled by changing the theory (thus, loosing the advantages of the linear theory), or extending the language, or using external functions. In this paper we consider the last approach and we propose an algebra and a calculus for constraint relational databases extended with external functions, formally proving their equivalence. In doing that, we use an approach similar to the one used by Klug to prove the equivalence between the relational algebra and the relational calculus extended with aggregate functions [14]. As far as we know, this is the first approach to introduce external functions in constraint query languages.