Peer-to-peer Collaboration over XML Documents

International audienceExisting solutions for the collaboration over XML documents are limited to a centralised architecture. In this paper we propose an approach for peer-to-peer collaboration over XML documents where users can work off-line on their document replica and synchronise in an ad-hoc manner with other users. Our algorithm for maintaining consistency over XML documents recursively applies the tombstone operational transformation approach over the document levels

Scalable XML Collaborative Editing with Undo

Commutative Replicated Data-Type (CRDT) is a new class of algorithms that ensure scalable consistency of replicated data. It has been successfully applied to collaborative editing of texts without complex concurrency control. In this paper, we present a CRDT to edit XML data. Compared to existing approaches for XML collaborative editing, our approach is more scalable and handles all the XML editing aspects : elements, contents, attributes and undo. Indeed, undo is recognized as an important feature for collaborative editing that allows to overcome system complexity through error recovery or collaborative conflict resolution.Le type de données répliqué commutatives (CRDT) est une nouvelle classe d'algorithmes qui assurent la cohérence des données répliquées tout en passant à l'échelle. Il a été appliqué avec succès à l'édition collaborative de textes sans mécanisme de contrôle de la concurrence complexe. Dans cet article, nous présentons un CRDT pour éditer des données XML. Par rapport aux approches existantes pour l'édition collaborative d'XML, notre approche offre un meilleur passage à l'échelle et gère tous les aspects de l'édition de document XML: éléments, le contenu, les attributs et l'annulation. En effet, l'annulation est reconnue comme un élément important pour l'édition collaborative qui permet de surmonter la complexité du système de collaboration grâce à la récupération d'erreur ou de résolution des conflits

Improving Textual Merge Result

International audienceIn asynchronous collaborative systems, merging is an essential component. It allows to reconcile modifications made concurrently as well as managing software change through branching. The collaborative system is in charge to propose a merge result that includes user's modifications. The users now have to check and adapt this result. The adaptation should be as effort-less as possible, otherwise, the users may get frustrated and will quit the collaboration. The objective of this paper is to improve the result quality of the textual merge tool that constitutes the default merge tool of distributed version control systems. The basic idea is to study the behavior of the concurrent modifications during merge procedure. We identified when the existing merge techniques under-perform, and we propose solutions to improve the quality of the merge. We finally compare with the traditional merge tool through a large corpus of collaborative editing

P2P Logging and Timestamping for Reconciliation

ISBN : 978-1-60558-306-8/08/08Dans VLDB 2008International audienceIn this paper, we address data reconciliation in peer-to-peer (P2P) collaborative applications. We propose P2P-LTR (Logging and Timestamping for Reconciliation) which provides P2P logging and timestamping services for P2P reconciliation over a distributed hash table (DHT). While updating at collaborating peers, updates are timestamped and stored in a highly available P2P log. During reconciliation, these updates are retrieved in total order to enforce eventual consistency. In this paper, we first give an overview of P2P-LTR with its model and its main procedures. We then present our prototype used to validate P2P-LTR. To demonstrate P2P-LTR, we propose several scenarios that test our solutions and measure performance. In particular, we demonstrate how P2P-LTR handles the dynamic behavior of peers with respect to the DHT

P2P Logging and Timestamping for Reconciliation

In this report, we address data reconciliation in peer-to-peer (P2P) collaborative applications. We propose P2P-LTR (Logging and Timestamping for Reconciliation) which provides P2P logging and timestamping services for P2P reconciliation over a distributed hash table (DHT). While updating at collaborating peers, updates are timestamped and stored in a highly available P2P log. During reconciliation, these updates are retrieved in total order to enforce eventual consistency. In this report, we first give an overview of P2P-LTR with its model and its main procedures. We then present our prototype used to validate P2P-LTR. To demonstrate P2P-LTR, we propose several scenarios that test our solutions and measure performance. In particular, we demonstrate how P2P-LTR handles the dynamic behavior of peers with respect to the DHT

Rethinking Consistency Management in Real-time Collaborative Editing Systems

Networked computer systems offer much to support collaborative editing of shared documents among users. Increasing concurrent access to shared documents by allowing multiple users to contribute to and/or track changes to these shared documents is the goal of real-time collaborative editing systems (RTCES); yet concurrent access is either limited in existing systems that employ exclusive locking or concurrency control algorithms such as operational transformation (OT) may be employed to enable concurrent access. Unfortunately, such OT based schemes are costly with respect to communication and computation. Further, existing systems are often specialized in their functionality and require users to adopt new, unfamiliar software to enable collaboration. This research discusses our work in improving consistency management in RTCES. We have developed a set of deadlock-free multi-granular dynamic locking algorithms and data structures that maximize concurrent access to shared documents while minimizing communication cost. These algorithms provide a high level of service for concurrent access to the shared document and integrate merge-based or OT-based consistency maintenance policies locally among a subset of the users within a subsection of the document – thus reducing the communication costs in maintaining consistency. Additionally, we have developed client-server and P2P implementations of our hierarchical document management algorithms. Simulations results indicate that our approach achieves significant communication and computation cost savings. We have also developed a hierarchical reduction algorithm that can minimize the space required of RTCES, and this algorithm may be pipelined through our document tree. Further, we have developed an architecture that allows for a heterogeneous set of client editing software to connect with a heterogeneous set of server document repositories via Web services. This architecture supports our algorithms and does not require client or server technologies to be modified – thus it is able to accommodate existing, favored editing and repository tools. Finally, we have developed a prototype benchmark system of our architecture that is responsive to users’ actions and minimizes communication costs

Merging By Decentralized Eventual Consistency Algorithms

International audienceMerging mechanism is an essential operation for version control systems. When each member of a collaborative development work on an individual copy of the project, software merging allows to reconcile modifications made concurrently as well as managing software change through branching. The collaborative system is in charge to propose a merge result that includes user's modifications. The users now have to check and adapt this result. The adaptation should be as effortless as possible, otherwise, the users may get frustrated and will quit the collaboration. The objective of this paper consists of studying the textual merge results during the collaboration by using specific algorithms, and propose a solution to improve the result quality of the textual merge produced by the default merge tool of distributed version control systems. Through a study of eight open-source repositories totaling more than 3 million lines of code, we observe the behavior of the concurrent modifications during the merge procedure. We identified when the existing merge techniques under-perform, and we propose solutions to improve the quality of the merge. We finally compare with the traditional merge tool through a large corpus of collaborative editing

Logoot: a P2P collaborative editing system

Massive collaborative editing becomes a reality through leading projects such as the Wikipedia. Such massive collaboration is currently supported with costly central service. To avoid such costs, we aim to provide a peer-to-peer collaborative editing system. Existing approaches that propose distributed collaborative distributed either do not scale in term of users number or in term of editions number. We present the Logoot approach that scales in these both dimensions while ensuring causality, consistency and intention criteria. We evaluate the Logoot approach and compare it to others with a corpus of all the editions applied on a set of the most edited and biggest page of the Wikipedia

Concurrency Control and Awareness Support for Multi-synchronous Collaborative Editing

International audienceCollaborative editing tools have become increasingly popular in the last decade, with some systems being used by massive numbers of users. While traditionally collaborative editing systems would either target synchronous or asynchronous collaboration settings, some recent systems support both types of collaboration, even supporting disconnected work. In this paper we analyze the limitations of existing systems and propose a data management solution that overcomes such limitations. The proposed concurrency control algorithm, based on conflict-free data types, builds on the ideas previously developed for synchronous collaboration, extending them to support asynchronous collaboration. Our solution also includes the necessary information for providing comprehensive awareness information to users. The evaluation of our algorithm shows that comparing our solution with traditional solutions in collaborative editing, the conflict resolution strategy proposed in this paper leads to results closer to the ones expected by users

A Comparison of Optimistic Approaches to Collaborative Editing of Wiki Pages

Wikis, a popular tool for sharing knowledge, are basically collaborative editing systems. However, existing wiki systems offer limited support for co-operative authoring, and they do not scale well, because they are based on a centralised architecture. This paper compares the well-known centralised MediaWiki system with several peer-to-peer approaches to editing of wiki pages: an operational transformation approach (MOT2), a commutativity-oriented approach (WOOTO) and a conflict resolution approach (ACF). We evaluate and compare them, according to a number of qualitative and quantitative metrics