Symmetric Relations and Cardinality-Bounded Multisets in Database Systems

In a binary symmetric relationship, A is related to B if and only if B is related to A. Symmetric relationships between k participating entities can be represented as multisets of cardinality k. Cardinality-bounded multisets are natural in several real-world applications. Conventional representations in relational databases suffer from several consistency and performance problems. We argue that the database system itself should provide native support for cardinality-bounded multisets. We provide techniques to be implemented by the database engine that avoid the drawbacks, and allow a schema designer to simply declare a table to be symmetric in certain attributes. We describe a compact data structure, and update methods for the structure. We describe an algebraic symmetric closure operator, and show how it can be moved around in a query plan during query optimization in order to improve performance. We describe indexing methods that allow efficient lookups on the symmetric columns. We...

• Type: Conference
• Year: 2004
• Where: VLDB
• Authors: Kenneth A. Ross, Julia Stoyanovich
• Keywords: Cardinality-bounded Multisets, Database, Symmetric, Symmetric Relationships, VLDB 2004