有别于传统分布式系统,实时协同编辑系统强调自然和谐的人人交互和人机交互,允许不同地点的协同用户同时编辑同一共享对象.为了给协同用户提供良好的响应性,实时协同编辑系统有必要采用全复制式体系结构,但又给共享对象的一致性维护问...有别于传统分布式系统,实时协同编辑系统强调自然和谐的人人交互和人机交互,允许不同地点的协同用户同时编辑同一共享对象.为了给协同用户提供良好的响应性,实时协同编辑系统有必要采用全复制式体系结构,但又给共享对象的一致性维护问题带来巨大挑战,这一直是协同计算学科的研究热点.近年研究重点逐步从结果一致性发展到操作意图一致性.该文以操作意图一致性为主线,对支持操作意图一致性的实时协同编辑算法进行深入和全面的比较、分析和总结.首先,以Lamport事件偏序关系为起点,对协同编辑系统的因果关系、简单并发关系和偏并发关系概念进行整理.同时,给出实时协同编辑系统中全序关系的分类,操作的全序和操作对象的全序.在对全序关系和优先级进行剖析的基础上,阐述了实时协同编辑系统中的三类一致性模型:CC(Causality-preservation,Convergence)模型、CCI(Causality-preservation,Convergence,Intention-preservation)模型和CA(Causalitypreservation,Admissibility)模型.特别地,文中按照因果一致性、结果一致性和操作意图一致性的分类,给出操作意图一致性的维护路线图.然后,分别综述了各类实时协同编辑算法的研究进展和现状,包括OT(Operational Transformation)算法、AST(Address Space Transformation)算法和CRDT(Commutative Replicated Data Type)算法.进一步,文中给出了各类操作意图一致性算法的基本原理和执行框架,并基于一个代表性协同工作场景和算例对典型算法进行详细解析.接下来,文中从操作意图一致性、支持操作意图一致性的典型算法、操作转换函数和算法时间复杂度这4个关键方面对实时协同编辑算法进行归纳和对比.最后对全文小结,并指出为了进一步发展实时协同编辑系统,未来还需要在优先级策略、算法伸缩性、复杂操作语义类型、粗粒度操作对象以及选择性撤销机制等方面深入开展一些研究工作.展开更多
Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy ...Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy for real-time distributed cooperative editing system. Moreover, operation transformation and data consistency maintenancetechnology are able to assure of quick response and unconstraint, but can't solve the context-specific inconsistencyproblems. Enlightened by the idea of operation transformation and optimistic locking mechanism, we bring forwardthe concurrency control algorithm of optimistic locking based on relative position. In this algorithm, the start positionof locking region and the position of operation are relative, and they are not transformed into absolute position untiloperations are sent to cooperative sites. Furthermore, any coeditor can edit in advance before his/her locking is con-firmed. If his/her locking is successful, the previous operations go into effect, or else undo these previous operations.We have analyzed the actual applications and can find that the possibility of undoing the previous editing operationsbecause of locking conflict is very little. So this concurrency controlling algorithm has virtues of quick response, nicedata consistency maintenance etc.展开更多
文摘有别于传统分布式系统,实时协同编辑系统强调自然和谐的人人交互和人机交互,允许不同地点的协同用户同时编辑同一共享对象.为了给协同用户提供良好的响应性,实时协同编辑系统有必要采用全复制式体系结构,但又给共享对象的一致性维护问题带来巨大挑战,这一直是协同计算学科的研究热点.近年研究重点逐步从结果一致性发展到操作意图一致性.该文以操作意图一致性为主线,对支持操作意图一致性的实时协同编辑算法进行深入和全面的比较、分析和总结.首先,以Lamport事件偏序关系为起点,对协同编辑系统的因果关系、简单并发关系和偏并发关系概念进行整理.同时,给出实时协同编辑系统中全序关系的分类,操作的全序和操作对象的全序.在对全序关系和优先级进行剖析的基础上,阐述了实时协同编辑系统中的三类一致性模型:CC(Causality-preservation,Convergence)模型、CCI(Causality-preservation,Convergence,Intention-preservation)模型和CA(Causalitypreservation,Admissibility)模型.特别地,文中按照因果一致性、结果一致性和操作意图一致性的分类,给出操作意图一致性的维护路线图.然后,分别综述了各类实时协同编辑算法的研究进展和现状,包括OT(Operational Transformation)算法、AST(Address Space Transformation)算法和CRDT(Commutative Replicated Data Type)算法.进一步,文中给出了各类操作意图一致性算法的基本原理和执行框架,并基于一个代表性协同工作场景和算例对典型算法进行详细解析.接下来,文中从操作意图一致性、支持操作意图一致性的典型算法、操作转换函数和算法时间复杂度这4个关键方面对实时协同编辑算法进行归纳和对比.最后对全文小结,并指出为了进一步发展实时协同编辑系统,未来还需要在优先级策略、算法伸缩性、复杂操作语义类型、粗粒度操作对象以及选择性撤销机制等方面深入开展一些研究工作.
文摘Traditional locking mechanism is fit for the concurrency controlling and data consistency maintenance undercentralized architecture, but its response is slow, so it can not be used as concurrency controlling strategy for real-time distributed cooperative editing system. Moreover, operation transformation and data consistency maintenancetechnology are able to assure of quick response and unconstraint, but can't solve the context-specific inconsistencyproblems. Enlightened by the idea of operation transformation and optimistic locking mechanism, we bring forwardthe concurrency control algorithm of optimistic locking based on relative position. In this algorithm, the start positionof locking region and the position of operation are relative, and they are not transformed into absolute position untiloperations are sent to cooperative sites. Furthermore, any coeditor can edit in advance before his/her locking is con-firmed. If his/her locking is successful, the previous operations go into effect, or else undo these previous operations.We have analyzed the actual applications and can find that the possibility of undoing the previous editing operationsbecause of locking conflict is very little. So this concurrency controlling algorithm has virtues of quick response, nicedata consistency maintenance etc.
