Browsing JCSCW Vol. 17 (2008) by Subject "consistency maintenance"
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- Journal ArticleA Multi-Versioning Scheme for Intention Preservation in Collaborative Editing Systems*(Computer Supported Cooperative Work (CSCW): Vol. 17, 2008) Xue, Liyin; Orgun, Mehmet A.; Zhang, KangAlthough the multi-version approach to consistency maintenance has been widely discussed and implemented in database systems, version control systems, and asynchronous groupware systems, its potential in real-time groupware systems is largely unexplored. Intention preservation is an important aspect of consistency maintenance in real-time collaborative editing systems, where multiple users cooperate with each other by concurrently editing the same document. The multi-version approach is supposed to be able to preserve individual users’ concurrent conflicting intentions. In this article, we propose a new multi-versioning scheme that can preserve not only concurrent conflicting intentions but also contextual intentions while achieving convergence of the document under editing. By extending an existing multi-versioning scheme to a general one that specifies the conditions for convergence, we decouple the discussion of convergence from that of intention preservation. By constraining the general scheme, we arrive at the novel scheme that guarantees to preserve users’ intentions. The correctness of the scheme has been formally verified. The design of an algorithm for consistent version composition and identification has been discussed in detail.
- Journal ArticleAn Approach to Ensuring Consistency in Peer-to-Peer Real-Time Group Editors(Computer Supported Cooperative Work (CSCW): Vol. 17, 2008) Li, Du; Li, RuiReal-time group editors allow distributed users to edit a shared document at the same time over a computer network. Operational transformation (OT) is a well accepted consistency control method in state-of-the-art group editors. Significant progress has been made in this field but there are still many open issues and research opportunities. In particular, established theoretic OT frameworks all require that OT algorithms be able to converge along arbitrary transformation paths. This property is desirable because group editors that implement such algorithms will not rely on a central component for achieving convergence. However, this has not been achieved in any published work to our knowledge. We analyze the root of this problem and propose a novel state difference based transformation (SDT) approach which ensures convergence in the presence of arbitrary transformation paths. Our approach is based on a novel consistency model that is more explicitly formulated than previously established models for proving correctness. SDT is the first and the only OT algorithm proved to converge in peer-to-peer group editors.
- Journal ArticleMulti-level Editing of Hierarchical Documents(Computer Supported Cooperative Work (CSCW): Vol. 17, 39783) Ignat*, Claudia-Lavinia; Norrie, Moira C.Collaborative editing enables a group of people to edit documents collaboratively over a computer network. Customisation of the collaborative environment to different subcommunities of users at different points in time is an important issue. The model of the document is an important factor in achieving customisation. We have chosen a tree representation encompassing a large class of documents, such as text, XML and graphical documents and here we propose a multi-level editing approach for maintaining consistency over hierarchical-based documents. The multi-level editing approach involves logging edit operations that refer to each node. Keeping operations associated with the tree nodes to which they refer offers support for tracking user activity performed on various units of the document. This facilitates the computation of awareness information and the handling of conflicting changes referring to units of the document. Moreover, increased efficiency is obtained compared to existing approaches that use a linear structure for representing documents. The multi-level editing approach involves the recursive application of any linear merging algorithm over the document structure and we show how the approach was applied for real-time and asynchronous modes of collaboration.