Conditions of efficient updates on network structures

Redundant network structures allow efficient retrievals. Procedures to design network structures that allow efficient retrievals [9] add redundancies into network structures. However, as redundancies increase, costs of updates increase. When network structures are redundant, costs of updates include costs of updating original data, checking consistencies, and updating derived data. This paper presents the super‐key condition to reduce the costs of checking consistencies in redundant network structures. First, constraints required to keep redundant network structures consistent are shown and then a sequence of processes to delete or insert a record in redundant network structures maintaining the constraints is given. Relationships between functional dependencies and updates are discussed to derive the super‐key condition. The condition classifies network structures regarding costs of the processes to delete or insert a record. Finally, a procedure to design network structures that satisfy the super‐key condition is given. The procedure may increase redundancies of network structures to reduce costs of updates.