Model Consistency for Distributed Collaborative Modeling

International audienceCurrent collaborative modeling tools use a centralized architecture , based on version control system, where models are updated asynchronously. These tools depend on a single server and are not completely adapted for collaborative modeling, where update reactivity is essential. In this paper, we propose a framework for building collabo-rative modeling tools which provides synchronous model update. The framework is based on a peer-to-peer architecture and uses a consistency algorithm for model updating

A New Distributed Transaction Protocol and Its Formal Analysis in Maude

Designers of distributed database systems face the choice between performance and consistency guarantees: with stronger consistency guarantees comes higher transactional latency and lower throughput. Certain collaborative editing application scenarios only require read atomicity (either all or none of a transaction's updates are visible to another transaction) and no lost updates (all updates are incrementally performed). Many existing distributed database systems meet these requirements. However, they all provide additional stronger consistency guarantees (such as causal consistency), and therefore incur lower performance. In this paper we define a new distributed transaction protocol, ROLA, that targets application scenarios where only read atomicity and no lost updates are needed. We formally model ROLA in Maude. We then perform model checking to analyze both the correctness and the performance of ROLA. For correctness, we use standard model checking to analyze ROLA's satisfaction of read atomicity and prevention of lost updates. Our results show that ROLA satisfies the correctness properties with a bounded number of parameters. To analyze performance we: (a) perform statistical model checking to analyze key performance properties such as throughput, averange latency, and commit rate; and (b) compare these performance results with those obtained by also modeling and analyzing in Maude the same performance properties for Walter, a well-known high-performance protocol meeting the requirements of read atomicity and preservation of lost updates. Our statistical model checking results show that ROLA outperforms Walter.Ope

Mixed reality participants in smart meeting rooms and smart home enviroments

Human–computer interaction requires modeling of the user. A user profile typically contains preferences, interests, characteristics, and interaction behavior. However, in its multimodal interaction with a smart environment the user displays characteristics that show how the user, not necessarily consciously, verbally and nonverbally provides the smart environment with useful input and feedback. Especially in ambient intelligence environments we encounter situations where the environment supports interaction between the environment, smart objects (e.g., mobile robots, smart furniture) and human participants in the environment. Therefore it is useful for the profile to contain a physical representation of the user obtained by multi-modal capturing techniques. We discuss the modeling and simulation of interacting participants in a virtual meeting room, we discuss how remote meeting participants can take part in meeting activities and they have some observations on translating research results to smart home environments

Proceedings of the ECSCW'95 Workshop on the Role of Version Control in CSCW Applications

The workshop entitled "The Role of Version Control in Computer Supported Cooperative Work Applications" was held on September 10, 1995 in Stockholm, Sweden in conjunction with the ECSCW'95 conference. Version control, the ability to manage relationships between successive instances of artifacts, organize those instances into meaningful structures, and support navigation and other operations on those structures, is an important problem in CSCW applications. It has long been recognized as a critical issue for inherently cooperative tasks such as software engineering, technical documentation, and authoring. The primary challenge for versioning in these areas is to support opportunistic, open-ended design processes requiring the preservation of historical perspectives in the design process, the reuse of previous designs, and the exploitation of alternative designs. The primary goal of this workshop was to bring together a diverse group of individuals interested in examining the role of versioning in Computer Supported Cooperative Work. Participation was encouraged from members of the research community currently investigating the versioning process in CSCW as well as application designers and developers who are familiar with the real-world requirements for versioning in CSCW. Both groups were represented at the workshop resulting in an exchange of ideas and information that helped to familiarize developers with the most recent research results in the area, and to provide researchers with an updated view of the needs and challenges faced by application developers. In preparing for this workshop, the organizers were able to build upon the results of their previous one entitled "The Workshop on Versioning in Hypertext" held in conjunction with the ECHT'94 conference. The following section of this report contains a summary in which the workshop organizers report the major results of the workshop. The summary is followed by a section that contains the position papers that were accepted to the workshop. The position papers provide more detailed information describing recent research efforts of the workshop participants as well as current challenges that are being encountered in the development of CSCW applications. A list of workshop participants is provided at the end of the report. The organizers would like to thank all of the participants for their contributions which were, of course, vital to the success of the workshop. We would also like to thank the ECSCW'95 conference organizers for providing a forum in which this workshop was possible

Exploring the use of local consistency measures as thresholds for dead reckoning update packet generation

Human-to-human interaction across distributed applications requires that sufficient consistency be maintained among participants in the face of network characteristics such as latency and limited bandwidth. Techniques and approaches for reducing bandwidth usage can minimize network delays by reducing the network traffic and therefore better exploiting available bandwidth. However, these approaches induce inconsistencies within the level of human perception. Dead reckoning is a well-known technique for reducing the number of update packets transmitted between participating nodes. It employs a distance threshold for deciding when to generate update packets. This paper questions the use of such a distance threshold in the context of absolute consistency and it highlights a major drawback with such a technique. An alternative threshold criterion based on time and distance is examined and it is compared to the distance only threshold. A drawback with this proposed technique is also identified and a hybrid threshold criterion is then proposed. However, the trade-off between spatial and temporal inconsistency remains