393 research outputs found
Framework for Real-time collaboration on extensive Data Types using Strong Eventual Consistency
La collaboration en temps réel est un cas spécial de collaboration où les utilisateurs travaillent sur le même élément simultanément et sont au courant des modifications des autres utilisateurs en temps réel. Les données distribuées doivent rester disponibles et consistant tout en étant répartis sur plusieurs systèmes physiques. "Strong Consistency"
est une approche qui crée un ordre total des opérations en utilisant des mécanismes tel que le "locking". Cependant, cela introduit un "bottleneck". Ces dix dernières années, les algorithmes de concurrence ont été étudiés dans le but de garder la convergence de tous les replicas sans utiliser de "locking" ni de synchronisation. "Operational Trans-
formation" et "Conflict-free Replicated Data Types (CRDT)" sont utilisés dans ce but. Cependant, la complexité de ces stratégies les rend compliquées à intégrer dans des logicielles conséquents, comme les éditeurs de modèles, spécialement pour des data structures complexes comme les graphes. Les implémentations actuelles intègrent seulement des data linéaires tel que le texte. Dans ce mémoire, nous présentons CollabServer, un framework pour construire des environnements de collaboration. Il a une implémentation de CRDTs pour des data structures complexes tel que les graphes et donne la possibilité de construire ses propres data structures.Real-time collaboration is a special case of collaboration where users work on the same artefact simultaneously and are aware of each other’s changes in real-time. Shared data should remain available and consistent while dealing with its physically distributed
aspect. Strong Consistency is one approach that enforces a total order of operations using mechanisms, such as locking. This however introduces a bottleneck. In the last decade, algorithms for concurrency control have been studied to keep convergence of all replicas without locking or synchronization. Operational Transformation and Conflict free Replicated Data Types (CRDT) are widely used to achieve this purpose. However, the complexity of these strategies makes it hard to integrate in large software, such as modeling editors, especially for complex data types like graphs. Current implementations only integrate linear data, such as text. In this thesis, we present CollabServer, a framework to build collaborative environments. It features a CRDTs implementation for
complex data types such as graphs and gives possibility to build other data structures
A component-based collaboration infrastructure
Groupware applications allow geographically distributed users to collaborate
on shared tasks. However, it is widely recognized that groupware applications are
expensive to build due to coordination services and group dynamics, neither of which
is present in single-user applications. Previous collaboration transparency systems
reuse existing single-user applications as a whole for collaborative work, often at
the price of inflexible coordination. Previous collaboration awareness systems, on
the other hand, provide reusable coordination services and multi-user widgets, but
often with two weaknesses: (1) the multi-user widgets provided are special-purpose
and limited in number, while no guidelines are provided for developing multi-user
interface components in general; and (2) they often fail to reach the desired level of flexibility in coordination by tightly binding shared data and coordination services.
In this dissertation, we propose a component-based approach to developing group-
ware applications that addresses the above two problems. To address the first prob-
lem, we propose a shared component model for modeling data and graphic user inter-
face(GUI) components of groupware applications. As a result, the myriad of existing
single-user components can be re-purposed as shared GUI or data components. An
adaptation tool is developed to assist the adaptation process.
To address the second problem, we propose a coordination service framework
which systematically model the interaction between user, data, and coordination
protocols. Due to the clean separation of data and control and the capability to dynamically "glue" them together, the framework provides reusable services such as
data distribution, persistence, and adaptable consistency control. The association
between data and coordination services can be dynamically changed at runtime.
An Evolvable and eXtensible Environment for Collaboration (EXEC) is built to
evaluate the proposed approach. In our experiments, we demonstrate two benefits of
our approach: (1) a group of common groupware features adapted from existing single-
user components are plugged in to extend the functionalities of the environment itself;
and (2)coordination services can be dynamically attached to and detached from these
shared components at different granules to support evolving collaboration needs
Collaborative Ontology Development — Distributed Architecture and Visualization
In this paper we present the architecture of the browser-based community-driven ontology engineering platform Ontoverse. We will present the architectural needs and designs for an extensible collaborative ontology platform as well as the current implementation based on tuplespaces. In this context we briefly introduce the SQLSpaces and the Semantic Web Application Toolkit (SWAT). To provide interactive collaborative means for editing, merging, and discussing about ontologies adequate visualization techniques are needed to support the ontology designers and ontology users. Therefore we introduce a visualization method called SmartTree that implements focus and context techniques
Developing Collaborative XML Editing Systems
In many areas the eXtensible Mark-up Language (XML) is becoming the standard exchange and data format. More and more applications not only support XML as an exchange format but also use it as their data model or default file format for graphic, text and database (such as spreadsheet) applications. Computer Supported Cooperative Work is an interdisciplinary field of research dealing with group work, cooperation and their supporting information and communication technologies. One part of it is Real-Time Collaborative Editing, which investigates the design of systems which allow several persons to work simultaneously in real-time on the same document, without the risk of inconsistencies.
Existing collaborative editing research applications specialize in one or at best, only a small number of document types; for example graphic, text or spreadsheet documents. This research investigates the development of a software framework which allows collaborative editing of any XML document type in real-time. This presents a more versatile solution to the problems of real-time collaborative editing.
This research contributes a new software framework model which will assist software engineers in the development of new collaborative XML editing applications. The devised framework is flexible in the sense that it is easily adaptable to different workflow requirements covering concurrency control, awareness mechanisms and optional locking of document parts. Additionally this thesis contributes a new framework integration strategy that enables enhancements of existing single-user editing
applications with real-time collaborative editing features without changing their source code
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Software lock elision for x86 machine code
More than a decade after becoming a topic of intense research there is no
transactional memory hardware nor any examples of software transactional memory
use outside the research community. Using software transactional memory in large
pieces of software needs copious source code annotations and often means
that standard compilers and debuggers can no longer be used. At the same time,
overheads associated with software transactional memory fail to motivate
programmers to expend the needed effort to use software transactional
memory. The only way around the overheads in the case of general unmanaged code
is the anticipated availability of hardware support. On the other hand, architects
are unwilling to devote power and area budgets in mainstream microprocessors to
hardware transactional memory, pointing to transactional memory being a
"niche" programming construct. A deadlock has thus ensued that is blocking
transactional memory use and experimentation in the mainstream.
This dissertation covers the design and construction of a software transactional
memory runtime system called SLE_x86 that can potentially break this
deadlock by decoupling transactional memory from programs using it. Unlike most
other STM designs, the core design principle is transparency rather than
performance. SLE_x86 operates at the level of x86 machine code, thereby
becoming immediately applicable to binaries for the popular x86
architecture. The only requirement is that the binary synchronise using known
locking constructs or calls such as those in Pthreads or OpenMP
libraries. SLE_x86 provides speculative lock elision (SLE) entirely in
software, executing critical sections in the binary using transactional
memory. Optionally, the critical sections can also be executed without using
transactions by acquiring the protecting lock.
The dissertation makes a careful analysis of the impact on performance due to
the demands of the x86 memory consistency model and the need to transparently
instrument x86 machine code. It shows that both of these problems can be
overcome to reach a reasonable level of performance, where transparent
software transactional memory can perform better than a lock. SLE_x86 can
ensure that programs are ready for transactional memory in any form, without
being explicitly written for it
Flexible consistency for wide area peer replication
technical reportThe lack of a flexible consistency management solution hinders P2P implementation of applications involving updates, such as read-write file sharing, directory services, online auctions and wide area collaboration. Managing mutable shared data in a P2P setting requires a consistency solution that can operate efficiently over variable-quality failure-prone networks, support pervasive replication for scaling, and give peers autonomy to tune consistency to their sharing needs and resource constraints. Existing solutions lack one or more of these features. In this paper, we describe a new consistency model for P2P sharing of mutable data called composable consistency, and outline its implementation in a wide area middleware file service called Swarm1. Composable consistency lets applications compose consistency semantics appropriate for their sharing needs by combining a small set of primitive options. Swarm implements these options efficiently to support scalable, pervasive, failure-resilient, wide-area replication behind a simple yet flexible interface. We present two applications to demonstrate the expressive power and effectiveness of composable consistency: a wide area file system that outperforms Coda in providing close-to-open consistency overWANs, and a replicated BerkeleyDB database that reaps order-of-magnitude performance gains by relaxing consistency for queries and updates
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