USING SEMANTICS PASSING TECHNIQUES TO PROCESS MULTILEVEL TRANSACTIONS
CCPP: 一个并发C++语言的设计与实现

Traditional read/write transaction model is machine-oriented, i.e., every operation of a transaction is described as a low level access to database, and the transaction has two layer: logical and physical layer. The logical layer is used to express operations to logical database, i.e., update or query to records; the physical layer is used to describe operations to pages of disks. Therefore, it can not capture semantics of applications effectively. The authors present a three layer transaction model, which is constructed by adding a Semantic layer on traditional transaction model. The layer can express various semantic information about application for transaction processing. They also design a concurrency control mechanism ML protocol based on the transaction model. The mechanism can exploit the semantics from semantic layer for scheduling subtransaction at lower level, that is, the semantics can be passed from high level to low level to reduce the ratio of conflicts. ML protocol can pass three kinds of semantics: parallelity, commutativity, and conflict. The schedules produced by ML protocol are serializable.