CONSISTENCY AND ORDERABILITY - SEMANTICS-BASED CORRECTNESS CRITERIA FOR DATABASES

The semantics of objects and transactions in database systems are investigated. User-defined predicates called consistency assertions are used to specify user programs. Three new correctness criteria are proposed. The first correctness criterion consistency is based solely on the users' specifications and admits nonserializable executions that are acceptable to the users. Integrity constraints of the database are maintained through consistency assertions. The second correctness criterion orderability is a generalization of view serializability and represents a weak notion of equivalence to a serial schedule. Finally, the third correctness criterion strong orderability is introduced as a generalization of conflict serializability. Unlike consistency, the notions of orderability allow users to operate in isolation as maintenance of the integrity constraints now becomes the responsibility of the database system.