Conflict is common in collaboration, and may have both negative and positive effects on collaborative work. Past research has focused on controlling negative aspects of conflict by preventing, eliminating or isolating conflicts, but done little on exploring positive aspects of conflict. In this paper, we contribute a novel creative conflict resolution (CCR) approach to address these issues in real-time collaborative editing systems. In addition to maintaining consistency, the CCR approach is able to create new results from conflicts, generate alternative solutions based on collective effects of conflict operations, and support users to choose suitable conflict solutions and conflict resolution policies according to their needs. The CCR approach provides not only a new way of resolving conflicts in real-time collaborative editing systems, but also a framework for supporting a range of existing conflict resolution strategies. Techniques and user interface issues related to the CCR approach and a prototype implementation are discussed in this paper.

Complex 3D digital media creation demands anytime and anywhere collaboration support. The CoMaya project aims to incorporate such advanced collaboration capabilities into Autodesk Maya. This paper reports some research findings and lessons we learned from extending the transparent adaptation approach from 2D office applications to 3D digital media design tools.

Constraints maintenance plays an important role in keeping the integrity and validity of models in UML software modeling. Constraints maintenance capabilities are reasonably adequate in UML modeling applications, but few work has been done to address the distributed constraints maintenance issue in collaborative UML modeling environments. In this paper, we propose a novel solution to the issue, which can retain the effects of all concurrent modeling operations even though they may cause constraints violations. We further contribute a distributed constraints maintenance framework, in which the solution is encapsulated as a generic engine to be mounted in a variety of single-user UML modeling applications for supporting distributed collaborative UML modeling and distributed constraints maintenance.

Recent advancements in collaboration technology have shown that it is possible to convert existing single-user applications into real-time collaborative applications without modifying the source codes of the single-user applications. Such conversion relies on the API (Application Programming Interface) provided by the single-user applications. Poorly designed APIs make such conversion difficult, inefficient, or even impossible. Until now, it is not well understood what features APIs should provide to facilitate conversion of single-user applications into collaborative applications. This paper presents recommendations of the features single-user application APIs should provide to facilitate conversion. The results are based on what we have learnt from converting Microsoft Visio, into real-time collaborative Visio (CoVisio), and our previous experience in building CoWord and CoPowerPoint.

Modeling is commonly used in the process of software development. UML (Unified Modeling Language) is a standard software modeling language and has been widely adopted for software analysis and design. As software systems are getting larger and more complex nowadays, software modeling using UML often requires collective and collaborative efforts from multiple software designers. In contrast, most of today's software modeling applications are still single-user-oriented and do not offer much help to coordinate interaction and collaboration among team members. In this paper, we will present the technical challenges and solutions in providing advanced collaboration capabilities and transparently integrating them into mainstream software modeling applications to effectively facilitate collaboration among geographically dispersed software designers. The work has been tested and demonstrated by the design of CoRSA (Collaborative Rational Software Architect) - an experimental collaborative software modeling prototype based on RSA, one of the most widely used commercial software modeling applications in the market

Single-user interactive computer applications are pervasive in our daily lives and work. Leveraging single-user applications for supporting multi-user collaboration has the potential to significantly increase the availability and improve the usability of collaborative applications. In this article, we report an innovative Transparent Adaptation (TA) approach and associated supporting techniques that can be used to convert existing and new single-user applications into collaborative ones, without changing the source code of the original application. The cornerstone of the TA approach is the operational transformation (OT) technique and the method of adapting the single-user application programming interface to the data and operation models of OT. This approach and supporting techniques were developed and tested in the process of transparently converting two commercial off-the-shelf single-user applications (Microsoft Word and PowerPoint) into real-time collaborative applications, called CoWord and CoPowerPoint, respectively. CoWord and CoPowerPoint not only retain the functionalities and “look-and-feel” of their single-user counterparts, but also provide advanced multi-user collaboration capabilities for supporting multiple interaction paradigms, ranging from concurrent and free interaction to sequential and synchronized interaction, and for supporting detailed workspace awareness, including multi-user telepointers and radar views. The TA approach and generic collaboration engine software component developed from this work are potentially applicable and reusable in adapting a wide range of single-user applications.

Effective interaction among participants is crucial to the success of a presentation. The workspace of a presentation, which is the presentation slides, is a natural and effective medium of interactions among presentation participants. However, due to the insufficient support from existing collaborative presentation systems, workspace-mediated interaction is inconvenient in presentations, especially in collaborative presentations. In this paper, we explore typical workspace-mediated interaction forms and analyze their characteristics. Based on this analysis, we present a series of approaches to supporting workspace-mediated interaction in the context of the CoPowerPoint system.

Object grouping is an effective means for managing the complexity in graphics editing. However, research on collaborative object grouping has not been adequate. In this paper, we contribute a novel collaborative object grouping technique, called CoGroup. CoGroup can achieve maximal combined effects among compatible operations and preserve all users' work in the face of conflict without the overhead of undoing and redoing conflict operations as in existing serialization approaches. CoGroup has been implemented in collaborative word processing (CoWord) and slide authoring (CoPowerPoint) systems and is generally applicable to a range of off-the-shelf commercial graphics applications, particularly CAD/CASE tools.

Telepointers are a real-time groupware interface feature to indicate where other users are pointing. None of existing telepointer techniques, however, is capable of tracking the reference object and preserving the relative position in the face of dynamic content and view changes in real-time collaborative document editing systems. In this paper, we report a novel object-associated telepointer (OAT) technique with the following features in the face of dynamic content and view changes: (1) relocating telepointers to track the reference object; (2) preserving the position relative to the reference object; and (3) providing feedback of the telepointer relocation to the local user with a virtual local cursor. The key technique for supporting OAT is to extend the operational transformation technique with a generic Refer operation to support adjusting the reference object position. The OAT technique has been implemented in the CoWord system based on the transparent adaptation approach so that it can provide the OAT support to a range of realtime collaborative applications.

Operational Transformation (OT) is a technique originally invented for supporting consistency maintenance in collaborative text editors. Word processors have much richer data types and more comprehensive operations than plain text editors. Among others, the capability of updating attributes of any types of object is an essential feature of all word processors. In this paper, we report an extension of OT for supporting a generic Update operation, in addition to Insert and Delete operations, for collaborative word processing. We focus on technical issues and solutions involved in transforming Updates for both consistency maintenance and group undo. A novel technique, called Multi-Version Single-Display (MVSD), has been devised to resolve conflict between concurrent Updates, and integrated into the framework of OT. This work has been motivated by and conducted in the CoWord project, which aims to convert MS Word into a real-time collaborative word processor without changing its source code. This OT extension is relevant not only to word processors but also to a range of interactive applications that can be modelled as editors.

Single-user interactive computer applications are pervasive in our daily lives and work. Leveraging single-user applications for multi-user collaboration has the potential to significantly increase the availability and improve the usability of collaborative applications. In this paper, we report an innovative transparent adaptation approach for this purpose. The basic idea is to adapt the single-user application programming interface to the data and operational models of the underlying collaboration supporting technique, namely Operational Transformation. Distinctive features of this approach include: (1) Application transparency: it does not require access to the source code of the single-user application; (2) Unconstrained collaboration: it supports concurrent and free interaction and collaboration among multiple users; and (3) Reusable collaborative software components: collaborative software components developed with this approach can be reused in adapting a wide range of single-user applications. This approach has been applied to transparently convert MS Word into a real-time collaborative word processor, called CoWord, which supports multiple users to view and edit any objects in the same Word document at the same time over the Internet. The generality of this approach has been tested by re-applying it to convert MS PowerPoint into CoPowerPoint.