Steven Xia

Transparent adaptation of single-user applications for multi-user real-time collaboration

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.

Leveraging single-user applications for multi-user collaboration: the coword approach

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.

Operational transformation for collaborative word processing

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.

integrating advanced collaborative capabilities into web-based word processors

With the development of new web technologies, web-based collaborative applications, exemplified by office applications, are emerging to take advantage of webs attractive features. We propose to plug a collaborative engine into web-based office applications so that advanced collaboration capabilities can be seamlessly integrated without compromising or modifying their conventional capabilities. This engine lies on application-independent data addressing and operation models to be reusable for a wide range of diverse applications without being modified. in this paper, we present a data addressing model for web-based word processors, which complies with the model used by the engine and shall lay a good foundation for investigating data addressing models for other web-based applications.

Object-associated telepointer for real-time collaborative document editing systems

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

Creative conflict resolution in realtime collaborative editing systems

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.

A collaborative table editing technique based on transparent adaptation

Tables are an efficient means to organize information. Collaboration is important for table editing. In this paper, we report an innovative technique, called CoTable, for supporting collaborative table editing in both table-centric and word-centric complex documents. This collaborative table editing technique is based on the Transparent Adaptation approach and hence applicable to commercial off-the-shelf single-user editing applications. Key technical elements of the CoTable technique include: (1) techniques for adapting a variety of table-related data address models, accessible from the single-user Application Programming Interface (API), to that of the underlying Operational Transformation (OT) technique; and (2) techniques for translating user-level table editing operations into the primitive operations supported by OT. The CoTable technique has been implemented in the CoWord system, and CoWord-specific table processing issues and techniques are discussed in detail as well.

Conflict resolution of Boolean operations by integration in real-time collaborative CAD systems

Boolean operations are widely used in CAD applications to construct complex objects out of primitive ones. Conflict resolution of Boolean operations is a special and challenging issue in real-time collaborative CAD systems, which allow a group of geographically dispersed users to jointly perform design tasks over computer networks. In this paper, we contribute a novel conflict resolution technique that can retain the effects of individual conflicting Boolean operations by integrating them. This technique, named as CRIBO (Conflict Resolution by Integration for Boolean Operations), is in a sharp contrast to other ones that either desert the effects of some operations or keep the effects of different operations in different versions of the design. It is particularly good for collaborative CAD applications, where integration of different mindsets is a main source of creation and innovation. This technique lays a good foundation for resolving conflicting operations in design-oriented collaborative applications that require collective wisdom and stimulus of creation.

Real-Time Collaborative Software Modeling Using UML with Rational Software Architect

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 todays 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

API design recommendations for facilitating conversion of single-user applications into collaborative applications

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.