3,236 research outputs found
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
Designing a commutative replicated data type
Commuting operations greatly simplify consistency in distributed systems.
This paper focuses on designing for commutativity, a topic neglected
previously. We show that the replicas of \emph{any} data type for which
concurrent operations commute converges to a correct value, under some simple
and standard assumptions. We also show that such a data type supports
transactions with very low cost. We identify a number of approaches and
techniques to ensure commutativity. We re-use some existing ideas
(non-destructive updates coupled with invariant identification), but propose a
much more efficient implementation. Furthermore, we propose a new technique,
background consensus. We illustrate these ideas with a shared edit buffer data
type
Distributed Wikis: A Survey
International audienceSUMMARY "Distributed Wiki" is a generic term covering various systems, including "peer-to-peer wiki," "mobile wiki," "offline wiki," "federated wiki" and others. Distributed wikis distribute their pages among the sites of autonomous participants to address various motivations, including high availability of data, new collaboration models and different viewpoint of subjects. Although existing systems share some common basic concepts, it is often difficult to understand the specificity of each one, the underlying complexities or the best context in which to use it. In this paper, we define, classify and characterize distributed wikis. We identify three classes of distributed wiki systems, each using a different collaboration model and distribution scheme for its pages: highly available wikis, decentralized social wikis and federated wikis. We classify existing distributed wikis according to these classes. We detail their underlying complexities and social and technical motivations. We also highlight some directions for research and opportunities for new systems with original social and technical motivations
Abstract unordered and ordered trees CRDT
Trees are fundamental data structure for many areas of computer science and
system engineering. In this report, we show how to ensure eventual consistency
of optimistically replicated trees. In optimistic replication, the different
replicas of a distributed system are allowed to diverge but should eventually
reach the same value if no more mutations occur. A new method to ensure
eventual consistency is to design Conflict-free Replicated Data Types (CRDT).
In this report, we design a collection of tree CRDT using existing set CRDTs.
The remaining concurrency problems particular to tree data structure are
resolved using one or two layers of correction algorithm. For each of these
layer, we propose different and independent policies. Any combination of set
CRDT and policies can be constructed, giving to the distributed application
programmer the entire control of the behavior of the shared data in face of
concurrent mutations. We also propose to order these trees by adding a
positioning layer which is also independent to obtain a collection of ordered
tree CRDTs
Building a collaborative peer-to-peer wiki system on a structured overlay
International audienceThe ever growing request for digital information raises the need for content distribution architectures providing high storage capacity, data availability and good performance. While many simple solutions for scalable distribution of quasi-static content exist, there are still no approaches that can ensure both scalability and consistency for the case of highly dynamic content, such as the data managed inside wikis. We propose a peer-to-peer solution for distributing and managing dynamic content, that combines two widely studied technologies: Distributed Hash Tables (DHT) and optimistic replication. In our âuniversal wikiâ engine architecture (UniWiki), on top of a reliable, inexpensive and consistent DHT-based storage, any number of front-ends can be added, ensuring both read and write scalability, as well as suitability for large-scale scenarios. The implementation is based on Damon, a distributed AOP middleware, thus separating distribution, replication, and consistency responsibilities, and also making our system transparently usable by third party wiki engines. Finally, UniWiki has been proved viable and fairly efficient in large-scale scenarios
UniWiki: A Reliable and Scalable Peer-to-Peer System for Distributing Wiki Applications
The ever growing request for digital information raises the need for content distribution architectures providing high storage capacity, data availability and good performance. While many simple solutions for scalable distribution of quasi-static content exist, there are still no approaches that can ensure both scalability and consistency for the case of highly dynamic content, such as the data managed inside wikis. In this paper, we propose a peer to peer solution for distributing and managing dynamic content, that combines two widely studied technologies: distributed hash tables (DHT) and optimistic replication. In our ``universal wiki'' engine architecture (UniWiki), on top of a reliable, inexpensive and consistent DHT-based storage, any number of front-ends can be added, ensuring both read and write scalability. The implementation is based on a Distributed Interception Middleware, thus separating distribution, replication, and consistency responsibilities, and also making our system usable by third party wiki engines in a transparent way. UniWiki has been proved viable and fairly efficient in large-scale scenarios
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Similarities, challenges and opportunities of wikipedia content and open source projects
Copyright @ 2012 John Wiley & Sons, Ltd.Several years of research and evidence have demonstrated that Open Source Software (OSS) portals often contain a large amount of software projects that simply do not evolve, developed by relatively small communities, struggling to attract a sustained number of contributors. These portals have started to
increasingly act as a storage for abandoned projects, and researchers and practitioners should try and point out how to take advantage of such content. Similarly, other online content portals (like Wikipedia) could be harvested for valuable content. In this paper we argue that, even with differences in the requested expertise, many projects reliant on content and contributions by users undergo a similar evolution, and follow similar patterns: when a project fails to attract contributors, it appears to be not evolving, or abandoned. Far from a negative finding, even those projects could provide valuable content that should be harvested and identified based on common characteristics: by using the attributes of âusefulnessâ and âmodularityâ we isolate valuable content in both Wikipedia pages and OSS projects
Total order in opportunistic networks
Opportunistic network applications are usually assumed to work only with unordered immutable messages, like photos, videos, or music files, while applications that depend on ordered or mutable messages, like chat or shared contents editing applications, are ignored. In this paper, we examine how total ordering can be achieved in an opportunistic network. By leveraging on existing dissemination and causal order algorithms, we propose a commutative replicated data type algorithm on the basis of Logoot for achieving total order without using tombstones in opportunistic networks where message delivery is not guaranteed by the routing layer. Our algorithm is designed to use the nature of the opportunistic network to reduce the metadata size compared to the original Logoot, and even to achieve in some cases higher hit rates compared to the dissemination algorithms when no order is enforced. Finally, we present the results of the experiments for the new algorithm by using an opportunistic network emulator, mobility traces, and Wikipedia pages.Peer ReviewedPostprint (author's final draft
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