A less constraint concurrency control and consistency maintaince in collaborative CAD system

A novel CRDT-based synchronization method for real-time collaborative CAD systems

The primary goals in a synchronous, real-time collaborative editing system (RTCES) involve ensuring a high level of concurrent access (editability) to users while maintaining the properties of the CCI model (consistency, causality-preservation, and intention-preservation). The field of RTCES research has advanced in techniques to overcome some of the challenges inherent in the support of synchronous editing of a shared document via Operational Transformation (OT), however current OT techniques require high message and storage costs. Their performances degrade as the storage for past operations into history buffers increases. In this paper, we present a novel algorithmic framework for history buffer reduction, which minimizes the size of the history of operations and reduces storage overheads. We show how this algorithm can be pipelined within a hierarchical document tree, enabling for further efficiency and opportunities for intention preservation — currently a hard problem. Further, we show how to distribute this algorithm in a peer-to-peer RTCES and present empirical simulation results that demonstrate the validity of our approach. Our contributions are breaking new grounds in the field of synchronous collaborative editing.

A new 3D platform is build in the self developed WebCAD system, used for multiple user collaborative design. As an extension of the WebCAD system, the collaborative 3D CAD system proposes a collaborative Boolean operation method. With the method complex physical objects can be easily obtained through Boolean operations of some elemental entities. With the new system, geographically distributed designers can design and edit 3D entities collaboratively on their own browsers. A three-tier architecture and an entity-based access control mechanism to settle confliction in collaborative design process are also employed in the system.

Collaborative editing (CE) has been an area of continuous research since early days of CSCW. Various CE systems have been studied in academia as research vehicles to investigate key technical issues in building advanced collaborative applications. In recent years, CE techniques have been increasingly adopted and further developed in industry for supporting real-world Internet or Cloud-based CE systems/services, such as Google Docs, Codoxware, IBM OpenCoWeb, Novell Vibe, and SubEthaEdit. This workshop aims to bring together CE academic researchers, industry developers, and end-users to discuss and exchange ideas on contemporary issues in researching, developing, and adopting CE systems. We have successfully organized this workshop annually at CSCW-related conferences. This year's workshop focuses on CE issues and techniques for supporting complex real-world documents (including but not limited to rich text, xml, spreadsheet, 2D/3D digital media, CAD, video, etc.), and evaluation of CE systems for such complex real-world documents.

Automatic Detection of Copies Divergence in Collaborative Editing Systems

Real-time Collaborative Editors (RCE) are a class of distributed systems based on the interaction of several users trying to edit simultaneously shared documents, such as articles, wiki pages and programming source code. Operational Transformation (OT) is considered as the efficient and safe method for consistency maintenance in the literature of collaborative editors. Indeed, it is aimed at ensuring copies convergence even though the users’s updates are executed in any order on different copies. Unfortunately, existing OT algorithms often fail to achieve this objective. Moreover, these algorithms have limited scalability with the number of users as they use vector timestamps to enforce causality dependency. In this paper, we present a novel coordination model for managing collaborative editing work in a scalable and decentralized fashion. It may be deployed easily on P2P networks as it supports dynamic groups where users can leave and join at any time.

The Operational Transformation (OT) approach, used in many collaborative editors, allows a group of users to concurrently update replicas of a shared object and exchange their updates in any order. The basic idea of this approach is to transform any received update operation before its execution on a replica of the object. This transformation aims to ensure the convergence of the different replicas of the object, even though the operations are executed in different orders. However, designing transformation functions for achieving convergence is a critical and challenging issue. Indeed, the transformation functions proposed in the literature are all revealed incorrect. In this paper, we investigate the existence of transformation functions for a shared string altered by insert and delete operations. From the theoretical point of view, two properties - named TP1 and TP2 - are necessary and sufficient to ensure convergence. Using controller synthesis technique, we show that there are some transformation functions which satisfy only TP1 for the basic signatures of insert and delete operations. As a matter of fact, it is impossible to meet both properties TP1 and TP2 with these simple signatures.

In this paper the realization method of collaborative CAD is introduced, How to synchronize model is one of the key technologies of achieving collaboration CAD. The incremental transmission algorithm of accurate CAD model based on changed primitives is presented for replicated collaborative CAD system in this paper, which reduces greatly amount of model data transmission during the process of collaborative CAD. This algorithm effectively achieves rapid transmission of the CAD model in synchronized collaborative design, and guarantees the synchronization of collaborative model.KeywordsCollaborative CADCAD ModelChanged PrimitivesReal Time Transmission

Collaborative CAD systems enabling collaboration in computer-aided design processes among distributed designers are gaining more and more attention. Yet, such systems, especially in support of collaborative assembly modeling, are hardly achievable. In an effort to bridge this gap, we are dedicated to developing a collaborative CAD system with aim at 3D assembly modeling. As part of this effort, this paper addresses one function module of the system, a Web-based Product Structure Manager, which enables the Collaborative Product Structure Management (CPSM) in collaborative assembly modeling. In particular, CPSM facilitates product data sharing among distributed designers and supports collaboration in product structure creation and modification. A bench clamp assembly is used as an example to illustrate the Product Structure Manager for supporting collaborative assembly modeling.

The concept of time in traditional distributed systems has been inherited in the Computer-Supported Collaborative Work (CSCW) literature. The following assumptions have generally been made: (1) Events are atomic and their durations do not matter. (2) Total ordering of events can be achieved by some mechanical algorithm. (3) The relationship between events is determined solely by time (causal relationship). However, we observe that these assumptions are not appropriate if the goal is to faithfully preserve user intentions in collaborative systems. In particular, we discuss why and how these assumptions should be relaxed or removed in the design of collaborative editing systems.

The focus of this paper is on evaluating the needs of distributed design reviews and establishing requirements on tools to support designer reviews. Specifically, this research explores the US Department of Defense acquisition process. This literature review and requirement generation explores the impact of Multi-User CAD (MUCAD) systems on collaborative design reviews and how quasi-asynchronous design reviews using MUCAD systems can enhance the understanding of product design. This paper describes synchronous and asynchronous design reviews to make a case for a combined approach that utilizes MUCAD systems. In this research, the generated requirements for a successful collaborative MUCAD system are divided into seven categories: concurrency, heterogeneity, annotations, IP protection, security, version control, and viewing. This paper serves as a guideline for future tests.

We are developing WFE, a system for Real-Time Collaborative Editing (RTCE) for existing Web pages. We aim to enable several users to perform simultaneous modifications on existing Web pages in their browsers, while modified contents are reflected to other users in real-time. In this paper, we present the application of WFE to a cloud computing environment as well as its advantages. The environment chosen is Google App Engine, which is a platform for developing Web applications. Our comparison experiments show that we can achieve this by using push technology to perform synchronization.

Collaborative editing systems allow multiple users to edit a shared document. They have transformed how interested parties cooperate to do work. The availability of free services such as Google Docs resulted in its increased popularity ultimately warranting attention from both academia and industry. The common implementation of such systems are based on existing infrastructures like the Internet which may be unreliable at best, if not totally unavailable, in challenging environments. In such situations, peer-to-peer (P2P) and delay tolerant networking (DTN) technologies can help provide communication among nodes. In this study, we develop the DTNDocs Android application to explore the possibility of developing a delay tolerant P2P collaborative editing system. The application uses IBR-DTN to communicate over a delay tolerant network and a modified LogootSplit algorithm for ensuring consistency in shared contents.

Collaborative graphics editing systems in ubiquitous environment support users to join and leave the collaboration dynamically at any time. The shared workspace state of these users will be inconsistent for the modification of the other session members. It is therefore necessary to initialize the application instance of the latecomer with the current state. In this paper, we propose a rejoining scheme that is based on the user interest prediction algorithm we proposed. The scheme is efficient for latecomers to rejoin the collaborative design session. The scheme is realized in our prototype system of collaborative graphics editing system that can work well in ubiquitous environments.

Network delays can cause serious usability problems in real-time collaborative environment. Network resources such as bandwidth, etc. are still the bottleneck in real-time collaborative environment. In addition, collaborative messages in groupware system may have different requirements for network QoS and different network protocols behave distinct performances on reliability and network delay aspects. Thus, it seems unreasonable to use a single protocol to send all interaction data. We did some experiments to investigate the impact on collaborating process which produced by packet size and network QoS requirement of different message type in collaborative graphics editing environment. According to the message characteristic, all messages are divided into several different types and for each type, suitable network protocols are used for exchanging information. Some experiments are made to test the usability of this integrated transmitting model.