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网构软件是指导Internet环境下协作式软件开发的一种新的软件范型,网构应用可以通过组合Internet上已有的web服务来方便地进行构造。事务机制是保障网构应用可靠性的重要技术。web服务的自治性及网构应用的长时间运行特性使得事务间的隔离性必须被放松,因而必须研究如何保障事务性网构应用在松弛隔离性下并发执行时的正确性。针对这一问题,提出了一种新的并发控制方法TSCM-CC(事务性服务复合模型-并发控制)来协调并发事务的相互影响。首先,根据依赖双方服务的事务特征对事务间依赖的类型进行细分;然后,提出了一系列的规则来限制依赖的动态形成,并证明了这些规则的正确性;最后,给出了这些规则的一个分布式的协调协议的实现机制。此方法的最大特色在于能够在保持各个事务性网构应用松弛原子性的同时保证松弛隔离性下并发执行的正确性。
Web-based software is a new paradigm of software that guides the development of collaborative software under the Internet environment. Web-based applications can be easily constructed by combining the existing web services on the Internet. Transaction mechanism is an important technology to ensure the reliability of network applications. The autonomy of web services and the long-running nature of web applications make the isolation between transactions must be relaxed. Therefore, we must study how to ensure the correctness of transactional web applications when they are concurrently executed under relaxed isolation. In response to this problem, a new concurrency control method TSCM-CC (Transactional Services Composite Model - Concurrency Control) is proposed to coordinate the interdependence of concurrent transactions. First, the types of interdependencies are subdivided according to the transactional features that depend on the services of both parties. Then, a series of rules are proposed to limit the dynamic formation of the dependencies and to prove the correctness of these rules. Finally, these rules are given The realization mechanism of a distributed coordination agreement. The most prominent feature of this method is that it can guarantee the correctness of concurrent execution under the condition of loose isolation while keeping the loose atomicity of each transactional network application.