Collaborative Editing Environment Based On The Tree Structure Of The Lock Operation Intention To Maintain

Consistency maintenance is a key research area in real-time collaborative editing system, which has always been paid great emphasis by researchers in the area. There exist two kinds of consistency in real-time collaborative editing system, one is syntactic consistency and the other is semantic consistency. Existing consistency maintenance techniques: operational transformation and address space transformation can effectively maintain the syntactic consistency of real-time collaborative editing system. As for semantic consistency, it needs to be maintained by locking. When locking is used to maintain the semantic consistency of real-time collaborative editing system, the consistency in locking itself also needs to be maintained. The intention preservation of locking is the most important and most complicated part of locking consistency maintenance. So the intention preservation of locking is vital to the maintenance of semantic consistency in real-time collaborative editing system.On the basis of analyzing exsiting work, in this paper we research the intention preservation of locking based on operational transformation and address space transformation. And our main research work is as follows:Firstly we put forward a locking intention preservation algorithm TreeLock_GOTO, which is based on operational transformation (OT). TreeLock_GOTO relies on a tree representation of the document and introduces optional locking to different granularity layers of the document. Compared with existing algorithm which uses a linear representation of the document, TreeLock_GOTO has not only maintained the intention of the locking operation, but also greatly improved the execution efficiency of locking transformation.Secondly we put forward a locking intention preservation algorithm TreeLock_AST which is based on Address Space Transformation (AST). Besides OT, AST is another important consistency maintenance technique in collaborative editing system, which can effectively maintain the syntactic consistency of collaborative editing system. In this paper, we further discover that AST can also preserve the intention of locking operation just like OT. Compared with TreeLock_GOTO, TreeLock_AST retraces the document's address space to the state when the locking operation is generated instead of modifying the operation itself. Then the locking operation can be executed directly in the retraced address space, which avoids the lost of relative position information between the operations in the transformation process. Besides the transformation of address space is more intuitive and closer to user's natural editing session.Finally we give the execution cases of both TreeLock_GOTO and TreeLock_AST and discuss the execution efficiency of both algorithms in details. We also design a system architecture of real-time collaborative editor which supports TreeLock_GOTO and TreeLock_AST.