Serialization of concurrent operations in a distributed collaborative environment

Abstract

In a distributed groupware system, objects shared by users are subject to concurrency and real-time constraints. In order to satisfy these, various concurrency control algorithms 141 [ 1 l] have been proposed that exploit the semantic properties of operations. By ordering concurrent operations, they guarantee consistency of the different copies of each object. The drawback of these algorithms is that in some situations they can result in inconsistent copies, a non-respect of user's intentions, and in the need to undo and redo certain operations.The principle objective of the this paper is to present an algorithm that overcomes these problems. The algorithm is based on the notion of user's intention, and also on the construction of equivalent histories by exploiting and combining some general semantic properties such as forward/backward transposition.

Symbolic Model-Checking of Optimistic Replication Algorithms

“…We can find, in the literature, several IT functions: [9] and Imine's algorithm [6]. Due to the lack of space, we report, here, only the IT function proposed by Ellis and Gibbs [4].…”

“…We have used the on-the-fly model-checker UPPAAL 9 to test the symbolic model proposed here. The Computation tree logic (CTL) formula [5] AG not Detected allows us to verify whether or not property T P 1 or T P 2 is satisfied.…”

“…The Computation tree logic (CTL) formula [5] AG not Detected allows us to verify whether or not property T P 1 or T P 2 is satisfied. We have considered several IT functions: Ellis [4], Ressel [8], Sun [12], Suleiman [9] and Imine [6]. To test different IT functions, it suffices to rewrite accordingly functions T ransf ormationCaseG(k) and T ransf ormationCase(k).…”

Customizable Collaborative Editor Relying on treeOPT Algorithm

“…The transformations are performed in such a manner that the intentions of the users are preserved and, at the end, the copies of the documents converge. Various operational transformation algorithms have been proposed: dOPT (Ellis and Gibbs, 1989), adOPTed (Ressel et al, 1996), GOT , GOTO (Sun and Ellis, 1998), SOCT2 (Suleiman et al, 1997;Suleiman et al, 1998), SOCT3 and SOCT4 (Vidot et al, 2000). Although these algorithms are generic operational transformation algorithms, they can be applied only for applications that use a linear representation of the document.…”

“…Starting with the dOPT algorithm of Ellis and Gibbs (1989), various algorithms using operational transformation for maintaining consistency in collaborative systems have been proposed: adOPTed (Ressel, 1996), GOT , GOTO (Sun and Ellis, 1998), SOCT2 (Suleiman et al, 1997), SOCT3 and SOCT4 (Vidot et al, 2000). As mentioned previously, all of these algorithms are based on a linear representation of the document whereas our algorithm uses a tree representation of the document and applies the same basic mechanisms as these algorithms recursively over the different document levels.…”