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|Title:||POLYGON JOIN DEPENDENCIES, CLOSED CO-RELATIONSHIP CHAINS AND THE CONNECTION TRAP IN RELATIONAL DATA BASES|
|Abstract:||Co-relationships between relations occur when both attributes supporting the relationship are non primary keys. A co-relationship can have at least three levels of semantic significance. A special case arises when relations are linked in a closed chain by co-relationships that have existential semantic significance. For binary relations in such a closed chain, it is shown that there is a fundamental theorem that prohibits extraction of reliable information from a complete join of the relations, unless the join contains a polygonal join dependency of order equal to the number of relations in the chain. Users who ignore this restriction fall into a sophisticated connection trap.|
|Appears in Collections:||Bradley, James|
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