An efficient consistency management algorithm for real-time mobile collaboration

Real time mobile collaboration involves two or more co-workers operating concurrently on a shared document using independent mobile devices. The replicated architecture is attractive for such applications since it does not rely on a central server and a user can continue to work on his or her own local document replica even during disconnection period. Several consistency management algorithms have been proposed, however the resource usage of such algorithms, which is critical in a mobile environment, has not been formally studied. Mobile devices are constrained in terms of memory and processing power, and operate in networking environments with limited bandwidth and transient connectivity. Therefore, algorithms that use resources more effectively improve the quality of the user experience in a mobile environment. ISO 9126-1 considers software to be efficient if it provides a balance between performance, and resource utilisation while performing its function. Therefore, this paper evaluates the efficiency of existing techniques, and proposes a more efficient consistency management algorithm. The new algorithm leverages existing techniques which are shown to be efficient and incorporates a novel history management strategy called partial history copy. Different combinations of these techniques are tested and compared to determine which one is most efficient and thus suitable for mobile usage

A groupware interface to a shared file system

Current shared file systems (NFS and SAMBA) are based on the local area network model. To these file systems, performance is the major issue. However, as the Internet grows, so does the distance between users and the Local Area Network. With this increase in distance, the latency increases as well. This creates a problem when multiple users attempt to work in a shared environment. Traditionally, the only way to collaborate over the Internet required the use of locks. These requirements motivated the creation of the State Difference Transformation algorithm that allows users non-blocking and unconstrained interaction across the Internet on a tree based structure. Fine Grain Locking, on the other hand, allows a user the ability to set a lock on a character or range of characters while using a form of the transformation algorithm listed above. This thesis proposes an implementation that integrates these two technologies as well as demonstrating the effectiveness and flexibility of State Difference Transformation. The implementation includes two applications that can be used to further research in both the transformation and locking communities. The first application allows users to create tests for SDT and Fine Grain Locking and verify the correctness of the algorithms in any given situation. The second application then furthers this research by creating a real-world groupware interface to a shared file system based on a clientserver architecture. This implementation demonstrates the usability and robustness of these algorithms in real world situations

A Constraint-based Approach for Generating Transformation Patterns

Undoing operations is an indispensable feature for many collaborative applications, mainly collaborative editors. It provides the ability to restore a correct state of shared data after erroneous operations. In particular, selective undo allows to undo any operation and is based on rearranging operations in the history thanks to the Operational Transformation (OT) approach. OT is an optimistic replication technique allowing for updating the shared data concurrently while maintaining convergence. It is a challenging task how to meaningfully combine OT and undo approaches. Indeed, undoing operations that are received and executed out-of-order at different sites leads to divergence cases. Even though various undo solutions have been proposed over the recent years, they are either limited or erroneous. In this paper, we propose a constraint-based approach to address the undo problem. We use Constraint Satisfaction Problem (CSP) theory to devise correct and undoable transformation patterns (w.r.t OT and undo properties) which considerably simplifies the design of collaborative objects.Comment: In Proceedings FOCLASA 2015, arXiv:1512.0694

Group Editer Using Graphical Operational Transformation

ABSTRACT KEYWORDS Graphical Operational transformation algorithm,G.O.T algorithm. 1. INTRODUCTION Collaborative editing system is which enables multiple users who reside remotely to share and edit some text / graphical / multimedia documents. This is an application area of Computer-supported cooperative work and it has been known for enhancing the efficiency and productivity of jobs and solving the physical limitation with virtualization[8] DESIGN REQUIREMENTS In this section we proposed and defined some of the underlying design requirements that we felt are important for a real-tim