【作者】 朱鸣；

【导师】 窦万峰；

【作者基本信息】 南京师范大学 ， 计算数学， 2007， 硕士

【摘要】 分布环境下的协同图形编辑系统OCES(Object-based Cooperative graphics Editing System)是计算机支持的协同工作CSCW(Computer Supported Cooperative Work)中一个十分活跃的研究方向。为了支持自然、自由的协同编辑，OCES具有分布的用户群、实时响应、协作透明性和无约束性等特征，为此大部分系统采用全复制的体系结构。研究与开发复制式体系结构下的OCES的关键问题之一是多个复制数据视图的一致性，这也是本文研究的核心。本文首先介绍了协同编辑系统的一致性维护技术。围绕协同编辑系统的一致性模型，具体讨论了一致性模型的三个一致性特征及可行的保证技术，并考察了一些典型的一致性维护策略。然后介绍了基于对象复制的多版本策略，在分析其多版本增创算法性能缺陷的基础上给出了基于冲突组概念的新的分布式多版本递增创建算法，减少了相容操作的比较次数、避免了版本冗余问题，提高了算法的性能。随后介绍了基于版本复制的多版本策略，其解决了对象复制策略所不能克服的一些复杂问题。提出了改进的基于版本复制多版本策略，实现了操作的层次存储，最大程度上避免了同一个操作被存储在多个版本中，减少了系统的操作存储量。最后简要分析了版本间冲突操作的产生情况，提出了使用子树构造法来保证版本间冲突操作的执行意愿，并首次提出了广义最大冲突组的概念，给出了一个利用广义最大冲突组实现版本间冲突操作的分布式算法。原型系统CoWork从系统实现的角度论证了上述策略和算法的正确性。文中还简要分析了CoWork涉及的其它支持策略，以及CoWork的系统性能。更多还原

【Abstract】 The Object-based Cooperative graphics Editing System (OCES) in distributed environment is now a very active research area of CSCW (Computer Supported Cooperative Work). To support free and natural interaction, this kind of system should have such characteristics as collaborative distribution, interactive in real-time and operation’s non-restriction. In order to satisfy these features, the fully replicated architecture should be adopted. One of the key problems in studying and designing the replicated collaborative editing system is the consistency of the multi-duplicated data view, and which is also the core discussed in this thesis.Technologies supporting consistency preservation based on a consistency model, which includes three consistency properties, are first surveyed. Our focus is how these properties are maintained. Several representative consistency schemes explored by other researchers are also introduced.Then a multi-versioning scheme based on object replication is discussed. Based on analysis of the performance limitation of the distributed algorithm for multiple versions incremental creation, a new algorithm using conflict set is proposesd which not only can decrease the comparison-number of compatible operations, but also can avoid the operation of removing the redundant object versions. The theory certification and simulation experiment results shows that performance of the new algorithm is more efficient than the original algorithm.Then a distributed collaborative multi-versioning scheme based on version replication, which can resolve some complex problems that the object-replication can not deal with, is discussed in detail. An improved multi-versioning using hierarchical storage strategy for operations is proposed to avoid same operation to be stored in different versions to the largest degree and reduce the number of operation stored in system.At last, this paper analyses the conflict operations between multi-versions, and proposes an idea of subtree construction to preserve the intention of these conflict operations. This paper first proposes a conception of generalized max conflict set, and uses it to realize the confict operation between muilti-versions.A prototype system CoWork is designed and implemented as a test-bed for the correctness of proposed strategies and algorithms. Other related cooperative techniques used in this prototype, as well as their runtime performance, are also discussed briefly in the end of this thesis.更多还原