Haifeng Shen

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.

Flexible notification for collaborative systems

Notification is an essential feature in collaborative systems, which determines a systems capability and flexibility in supporting different kinds of collaborative work. In the past years, various notification strategies have been designed for different systems. However, the design of notification components has been ad hoc, and the techniques used for supporting notification have been application-dependent. In this paper, we contribute a flexible notification framework that can be used to describe and compare a range of notification strategies used in existing collaborative systems, and to guide the design of notification components for new collaborative systems. The framework has been applied to the design of a notification component for a group editor, which uses a single notification mechanism to support various notification policies for meeting both real-time and non-real-time collaboration needs. In addition, a new operational transformation control algorithm has been devised in combination with the notification component, which is significantly simpler and more efficient than existing algorithms.

Flexible Merging for Asynchronous Collaborative Systems

Version control systems are widely used asynchronous collaborative systems in team-working environments, where document merging is a key function. However most existing systems only support limited semantic merging, and techniques for supporting semantic merging are strictly bound up with the merging algorithms that do syntactic merging. In this paper, we propose a flexible merging framework in which semantic merging policies are separated from the syntactic merging mechanism for asynchronous collaborative systems. In this framework, semantic merging policies are not restricted by the merging algorithms used in the syntactic merging mechanism, and the syntactic merging mechanism is flexible to support a wide range of semantic merging policies. This framework can be used to describe and compare a range of existing merging policies and mechanisms, and to guide the design of new merging policies and mechanisms. The proposed framework has been applied to the design of a flexible merging component in FORCE (Flexible Operation-based Revision Control Environment) prototype, which uses a single syntactic merging mechanism to support a range of semantic merging policies.

An Efficient and Reliable Geographic Routing Protocol Based on Partial Network Coding for Underwater Sensor Networks

Efficient routing protocols for data packet delivery are crucial to underwater sensor networks (UWSNs). However, communication in UWSNs is a challenging task because of the characteristics of the acoustic channel. Network coding is a promising technique for efficient data packet delivery thanks to the broadcast nature of acoustic channels and the relatively high computation capabilities of the sensor nodes. In this work, we present GPNC, a novel geographic routing protocol for UWSNs that incorporates partial network coding to encode data packets and uses sensor nodes’ location information to greedily forward data packets to sink nodes. GPNC can effectively reduce network delays and retransmissions of redundant packets causing additional network energy consumption. Simulation results show that GPNC can significantly improve network throughput and packet delivery ratio, while reducing energy consumption and network latency when compared with other routing protocols.

A log compression algorithm for operation-based version control systems

Version control systems are widely used to support distributed concurrent software development, where document merging is a key function. Most existing systems adopt state-based merging, which relies on the derivation of deltas among documents. The derivation of deltas involves transferring documents over the network and executing time-consuming text differentiation algorithms, which may result in a poor system response. Operation-based merging saves executed operations in logs as deltas, thus eliminating the need for deriving deltas. However, for the operation-based merging to be adopted in version control systems, a major technical challenge is how to keep the size of logs small so that it requires less time to transfer the log over the network and to re-execute operations in the log. In this paper we contribute a novel compression algorithm, which is able to minimize the size of a log as well as the number of operations within it. It has been proven both correct and complete in the sense that the compressed log has the same effect as the original one and operations that can be merged have already been merged.

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.

A complete textual merging algorithm for software configuration management systems

Software configuration management (SCM) systems are very important for coordinating group efforts in developing large and complex software systems. The ability to support concurrent software development is the key to deliver high quality software with low time-to-market, where merging is the core enabling technique. Textual merging is the primary and the only successful merging function available in todays SCM systems. However none of them supports complete textual merging, which is not only very useful itself but also the foundation for syntactic and semantic textual merging. In this paper we propose a novel operation-based textual merging algorithm, which has the capability of supporting complete textual merging while still preserving the intentions of individual editing operations

ATCoPE: any-time collaborative programming environment for seamless integration of real-time and non-real-time teamwork in software development

Real-time collaborative programming and non-real-time collaborative programming are two classes of methods and techniques for supporting programmers to jointly conduct complex programming work in software development. They are complementary to each other, and both are useful and effective under different programming circumstances. However, most existing programming tools and environments have been designed for supporting only one of them, and little has been done to provide integrated support for both. In this paper, we contribute a novel Any-Time Collaborative Programming Environment (ATCoPE) to seamlessly integrate conventional non-real-time collaborative programming tools and environments with emerging real-time collaborative programming techniques and support collaborating programmers to work in and flexibly switch among different collaboration modes according to their needs. We present the general design objectives for ATCoPE, the system architecture, functional design and specifications, rationales beyond design decisions, and major technical issues and solutions in detail, as well as a proof-of-concept implementation of the ATCoEclipse prototype system.

Achieving Data Consistency by Contextualization in Web-Based Collaborative Applications

Recent years have witnessed the emergence and rapid development of collaborative Web-based applications exemplified by Web-based office productivity applications. One major challenge in building these applications is maintaining data consistency while meeting the requirements of fast local response, total work preservation, unconstrained interaction, and customizable collaboration mode. These requirements are important in determining users’ experiences in interaction and collaboration, and in meeting users’ diverse needs under complex and dynamic collaboration and networking environments; but none of existing solutions is able to meet all of them. In this article, we present a data consistency maintenance solution capable of meeting these requirements for collaborative Web-based applications. Major technical contributions include an efficient sequence-based operation transformation control algorithm based on the concept of contextualization, an operation broadcast protocol for supporting a variety of collaboration modes, an operation replaying algorithm for ensuring fast local response and efficient remote operation replay, and a set of communication protocols for managing the integrity of collaborative Web-based sessions. The proposed solution has been implemented in a prototype collaborative Web-based editor WRACE and the correctness of the solution is formally verified in the article.