The functional data model and the data languages DAPLEX
ACM Transactions on Database Systems (TODS)
Testing implications of data dependencies
ACM Transactions on Database Systems (TODS)
Decomposition—a strategy for query processing
ACM Transactions on Database Systems (TODS)
Equivalence of Relational Algebra and Relational Calculus Query Languages Having Aggregate Functions
Journal of the ACM (JACM)
An extended relational algebra with control over duplicate elimination
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
Incremental maintenance of views with duplicates
SIGMOD '95 Proceedings of the 1995 ACM SIGMOD international conference on Management of data
On Multisets in Database Systems
WMP '00 Proceedings of the Workshop on Multiset Processing: Multiset Processing, Mathematical, Computer Science, and Molecular Computing Points of View
On a characterization of fuzzy bags
IFSA'03 Proceedings of the 10th international fuzzy systems association World Congress conference on Fuzzy sets and systems
RL-bags: A conceptual, level-based approach to fuzzy bags
Fuzzy Sets and Systems
Foundations of rule-based query answering
RW'07 Proceedings of the Third international summer school conference on Reasoning Web
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We argue that a multirelation (relation with duplicates) is not, a semantically independent data object, but rather it should be viewed as a sub- set of columns within a larger relation that has no duplicates. Consequently, at the level of the con- ceptual database, duplicates in base relations or in views are not allowed, nor are operations on mul- tirelations. Multirelations as query output can be specified by designating a subset of some relation's columns for output, while "hiding" the rest of the columns. Similarly, aggregate functions are applied to multirelations by applying them to a column within a relation. Our approach can be applied to extend any query language in a consistent way to have full multirelational expressiveness, and such an extension for the query language QUEL is detailed.