A multi-user selective undo/redo approach for collaborative CAD systems

AbstractThe engineering design process is a creative process, and the designers must repeatedly apply Undo/Redo operations to modify CAD models to explore new solutions. Undo/Redo has become one of most important functions in interactive graphics and CAD systems. Undo/Redo in a collaborative CAD system is also very helpful for collaborative awareness among a group of cooperative designers to eliminate misunderstanding and to recover from design error. However, Undo/Redo in a collaborative CAD system is much more complicated. This is because a single erroneous operation is propagated to other remote sites, and operations are interleaved at different sites. This paper presents a multi-user selective Undo/Redo approach in full distributed collaborative CAD systems. We use site ID and State Vectors to locate the Undo/Redo target at each site. By analyzing the composition of the complex CAD model, a tree-like structure called Feature Combination Hierarchy is presented to describe the decomposition of a CAD model. Based on this structure, the dependency relationship among features is clarified. B-Rep re-evaluation is simplified with the assistance of the Feature Combination Hierarchy. It can be proven that the proposed Undo/Redo approach satisfies the intention preservation and consistency maintenance correctness criteria for collaborative systems

User Participation and Tailorability in PSN Systems Design

User participation has received significant research attention in the past. Researchers have attempted to understand and demonstrate a link between user participation and system success, but studies have shown the link to be conditional. The purpose of this paper is to propose a type of system design when user participation is not required because the design consists of tailorable functionality, permits exploration through reversibility, and builds trust. In this paper past participation research is examined – including findings casting doubt on the participation-success link. Technology features are then offered to address unresolved user concerns identified in prior research. Future research of a non-participatory design in a Public Safety Network is also described. This paper contributes to IS design knowledge by expanding on the contingency view of user participation and system success. This paper also assists public safety professionals by offering potential design solutions to address user concerns

An analysis framework for CSCW systems

Software toolkits are under development to help construct applications that support group-working. Toolkit developers adopt different approaches to group-work support in order to tackle different issues and a toolkit is commonly characterised by the approach adopted. It is difficult to compare toolkits because of this lack of apparent commonality and it is difficult to decide which toolkits meet specific application requirements. [Continues.

Investigations of collaborative design environments: A framework for real-time collaborative 3D CAD

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This research investigates computer-based collaborative design environments, in particular issues of real-time collaborative 3D CAD. The thesis first presents a broad perspective of collaborative design environments with a preliminary case study of team design activities in a conventional and a computer mediated setting. This study identifies the impact and the feasibility of computer support for collaborative design and suggests four kinds of essential technologies for a successful collaborative design environment: information-sharing systems, synchronous and asynchronous co- working tools, project management systems, and communication systems. A new conceptual framework for a real-time collaborative 3D design tool, Shared Stage, is proposed based upon the preliminary study. The Shared Stage is defined as a shared 3D design workspace aiming to smoothly incorporate shared 3D workspaces into existing individual 3D workspaces. The addition of a Shared Stage allows collaborating designers to interact in real-time and to have a dynamic and interactive exchange of intermediate 3D design data. The acceptability of collaborative features is maximised by maintaining consistency of the user interface between 3D CAD systems. The framework is subsequently implemented as a software prototype using a new software development environment, customised by integrating related real-time and 3D graphic software development tools. Two main components of the Shared Stage module in the prototype, the Synchronised Stage View (SSV) and the Data Structure Diagram (DSD), provide essential collaborative features for real-time collaborative 3D CAD. These features include synchronised shared 3D representation, dynamic data exchange and awareness support in 3D workspaces. The software prototype is subsequently evaluated to examine the usefulness and usability. A range of quantitative and qualitative methods is used to evaluate the impact of the Shared Stage. The results, including the analysis of collaborative interactions and user perception, illustrate that the Shared Stage is a feasible and valuable addition for real-time collaborative 3D CAD. This research identifies the issues to be addressed for collaborative design environments and also provides a new framework and development strategy of a novel real-time collaborative 3D CAD system. The framework is successfully demonstrated through prototype implementation and an analytical usability evaluation.Financial support from the Department and from the UK government through the Overseas Research Studentship Awards

Assistierte Informationsanzeige in Smart Meeting Rooms

Ziel dieser Arbeit ist es, Konzepte für eine assistierte Informationsanzeige in Smart Meeting Rooms bereitzustellen. Dafür werden 3 Modelle erarbeitet. Hierauf basierend wird das Austauschen von Inhalten zwischen mehreren Geräten und das automatische Verteilen und Anordnen von Views auf unterschiedlichen Displays adressiert. Ein Ansatz zur interaktiven, bedarfsgerechten Erzeugung von neuen Darstellungen wird vorgestellt. Manuelles Anpassen der Anzeige und die Suche nach semantisch passenden Inhalten wird durch Hilfsmittel unterstützt. Eine situationsangepasste Assistenz wird beschrieben

Computer Supported Cooperative Work Applications for the Design of Buildings based on an integrated Building Model Management

Gegenstand der vorliegenden Arbeit ist die Konzeption und prototypische Umsetzung von Techniken des Computer Supported Cooperative Work (CSCW) im Rahmen einer integrierten objektorientierten und dynamischen Bauwerksmodellverwaltung zur Unterstützung der Bauwerksplanung. Die Planung von Bauwerken ist durch einen hohen Grad an Arbeitsteiligkeit, aber auch durch eine schwache Strukturierung der ablaufenden Prozesse gekennzeichnet. Besonders durch den Unikatcharakter des Planungsgegenstands \'Bauwerk\' ergeben sich signifikante Unterschiede zum Entwurf anderer, durch Serienfertigung produzierter Industriegüter. Zunehmend wird die Planung von Bauwerken in Virtual Enterprises ausgeführt, die sich durch eine dynamische Organisationsstruktur, geographische Verteilung der Partner, schwer normierbare Informationsflüsse und eine häufig stark heterogene informationstechnische Infrastruktur auszeichnen. Zur rechnerinternen Repräsent! ation des Planungsgegenstands haben sich objektorientierte Bauwerksmodelle bewährt. Aufgrund der Veränderlichkeit der Bauwerke und deren rechnerinterner Repräsentation im Laufe des Bauwerkslebenszyklus ist eine dynamische Anpassung der Modelle unumgänglich. Derartige in Form von Taxonomien dargestellte dynamische Bauwerksmodellstrukturen können gemeinsam mit den in Instanzform vorliegenden konkreten Projektinformationen in entsprechenden Modellverwaltungssystemen (MVS) gehandhabt werden. Dabei wird aufgrund der Spezialisierung und Arbeitsteilung im Planungsprozess von einer inhaltlich verknüpften Partialmodellstruktur, die räumlich verteilt sein kann, ausgegangen. Die vorgeschlagenen Methoden zur Koordinierung der Teamarbeit in der Bauwerksplanung beruhen auf der Nutzung von CSCW–Techniken für \'Gemeinsame Informationsräume\' und \'Workgroup Computing\', die im Kontext der als Integrationsbasis fungierenden Modellverwaltungssysteme umgesetzt werden. Dazu werden die zur d! ynamischen Bauwerksmodellierung erforderlichen Metaebenenfunk! tionalitäten sowie Ansätze zur Implementierung von Modellverwaltungskernen systematisiert. Ebenso werden notwendige Basistechniken für die Realisierung von MVS untersucht und eine Architektur zur rollenspezifischen Präsentation dynamischer Modellinhalte vorgestellt. Da klassische Schichtenmodelle nicht auf die Verhältnisse in Virtual Enterprises angewendet werden können, wird eine physische Systemarchitektur mit einem zentralen Projektserver, Domänenservern und Domänenclients vorgestellt. Ebenso werden Techniken zur Sicherung des autorisierten Zugriffs sowie des Dokumentencharakters beschrieben. Zur Unterstützung der asynchronen Phasen der Kooperation wird der gemeinsame Informationsraum durch Mappingtechniken zur Propagation und Notifikation von Änderungsdaten bezüglich relevanter Modellinformationen ergänzt. Zur Unterstützung synchroner Phasen werden Techniken zur Schaffung eines gemeinsamen Kontexts durch relaxierte WYSIWIS–Präsentationen auf Basis der Modellinformationen! verbunden mit Telepresence–Techniken vorgestellt. Weiterhin werden Methoden zur Sicherung der Group–Awareness für alle Kooperationsphasen betrachtet.The thesis covers the conceptual design and the prototypical realisation of Computer Supported Cooperative Work (CSCW)– techniques within the scope of an integrated, object-oriented, dynamic model management system for the support of building planning activities. The planning of buildings is characterised by a high degree of collaboration but by a weak structuring of the processes, too. Significant differences between the design of buildings and industrial goods produced by series production are implied by the uniqueness of a building. Increasingly, the planning of buildings is accomplished by Virtual Enterprises. These are characterised by a dynamic organisation structure, geographic dispersion of the involved planning experts, information flows, which are hard to standardise, and a frequently very heterogeneous information-technology infrastructure. Object oriented building models have proven to be a suitable base for! the binary representation of planning subject information. Due to the changeability of both building structures and their binary representation during the building life cycle, a dynamical adaptation of the models is indispensable. Dynamic building models, which are represented by taxonomic information, can be handled together with actual project information, which is stored in taxonomy instances within an appropriate model management system. Due to the specialisation and the division of labour in the planning process, a semantic linked but spatial distributed partial model structure is applied. The recommended methods for the coordination of teamwork in the planning process are based on the application of CSCW-techniques for \'Shared Information Spaces\' and \'Workgroup Computing\' in the context of model management systems acting as an foundation for planning information integration. The required meta level functionalities for dynamic building modelling and appropriate! implementation approaches for modelling kernels are systemat! ised. The necessary base techniques for the realisation of model management systems are explored. An architecture for the role specific presentation of dynamic model content is introduced, too. Due to the inadequacy of conventional multi-tier models for an application in Virtual Enterprises, an appropriate physical system architecture with a central project server, domain servers and domain clients is introduced. The thesis covers techniques, which ensure the authorised access to information and the authenticity of planning documents, too. For an adequate support of the asynchronous phases of collaboration, the Shared Information Space is supplied with mapping mechanisms for the propagation and user notification of changes in the relevant planning information. Synchronous collaboration can be performed by means of relaxed WYSIWIS-presentations connected with telepresence mechanisms in order to create a shared context for the planners. Furthermore, methods for the provis! ion of group-awareness for all co-operation phases are treated

A Taxonomy of workgroup Computing Applications

The goal of workgroup computing is to help individuals and groups efficiently perform a wide range of functions on networked computer systems (Ellis, Gibbs, & Rein, 1991). Early workgroup computing tools were designed for limited functionality and group interaction (Craighill, 1992). Current workgroup computing applications do not allow enough control of group processes and they provide little correlation between various workgroup computing application areas (Rodden and Blair, 1991). An integrated common architecture may produce more effective workgroup computing applications. Integrating common support functions into a common framework will avoid duplication of these functions for each workgroup computing application (Pastor & Jager, 1992). Over 50 research and commercial workgroup computing applications were analyzed to understand and discover their distinctive characteristics and fundamental structure. Using the specified methods, a detailed section of a workgroup computing taxonomy was synthesized for each of 11 workgroup computing functional areas. The detailed taxonomy was the consolidation of all the hierarchical structures. The taxonomy formed the basis for developing an integrated workgroup computing architecture and a set of workgroup computing Application Programming Interface (API) specifications. The results of this study support the hypothesis that the available workgroup computing literature and application documentation would provide sufficient information to develop a comprehensive workgroup computing taxonomy. By comparing workgroup tasks with workgroup computing functional areas, it was possible to derive a common set of workgroup computing management and support tasks that were based on the detailed workgroup computing taxonomy. Common workgroup computing management and support tasks formed the basis for a1! Integrated workgroup computing architecture. Finally, 86 new API specifications were written for common workgroup computing management and support functions. This study can be used by workgroup application developers to determine which common workgroup computing functions should be integrated into future workgroup applications. Implementing the results of this study in future workgroup computing systems will lead to flexible and integrated systems that are easier to use and more transparent to workgroup members. Workgroup computing researchers can use this study to identify workgroup computing functions that should be included in their research areas

Towards self-optimizing frameworks for collaborative systems

Two important performance metrics in collaborative systems are local and remote response times. For certain classes of applications, it is possible to meet response time requirements better than existing systems through a new system without requiring hardware, network, or user-interface changes. This self-optimizing system improves response times by automatically making runtime adjustments to three aspects of a collaborative application. One of these aspects is the collaboration architecture. Previous work has shown that dynamically switching architectures at runtime can improve response times; however, no previous work performs the switch automatically. The thesis shows that (a) another important performance parameter is whether multicast or unicast is used to transmit commands, and (b) response times can be noticeably better with multicast than with unicast when transmission costs are high. Traditional architectures, however, support only unicast - a computer that processes input commands must also transmit commands to all other computers. To support multicast, a new bi-architecture model of collaborative systems is introduced in which two separate architectures govern the processing and transmission tasks that each computer must perform. The thesis also shows that another important performance aspect is the order in which a computer performs these tasks. These tasks can be scheduled sequentially or concurrently on a single-core, or in parallel on multiple cores. As the thesis shows, existing single-core policies trade-off noticeable improvements in local (remote) for noticeable degradations in remote (local) response times. A new lazy policy for scheduling these tasks on a single-core is introduced that trades-off an unnoticeable degradation in performance of some users for a much larger noticeable improvement in performance of others. The thesis also shows that on multi-core devices, the tasks should always be scheduled on separate cores. The self-optimizing system adjusts the processing architecture, communication architecture, and scheduling policy based on response time predictions given by a new analytical model. Both the analytical model and the self-optimizing system are validated through simulations and experiments in practical scenarios