Abstract. Research in collaborative editing tends to have been undertaken in isolation rather than as part of a general information or application infrastructure. Our goal is to develop a universal information platform that can support collaboration in a range of application domains. Since not all user groups have the same conventions and not all tasks have the same requirements, this implies that it should be possible to customize the collaborative editor at the level of both communities and individual tasks. One of the keys to customization is to use a structured rather than linear representation of documents that can be applied to both textual and graphical editors. In this paper, we propose the treeOPT (tree OPerational Transformation) algorithm that, relying on a tree representation of documents, applies the operational transformation mechanism recursively over the different document levels. Applications using this algorithm achieve better efficiency, the possibility of working at different granularity levels and improvements in the semantic consistency.

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Many hypermedia models have been proposed, including those specifically developed to model navigational aspects of web sites. But few hypermedia systems have been implemented based on metamodelling principles familiar to the database community. Often there is no clear separation between conceptual and technical issues in the models and their implementations are not based on an explicit representation of a metamodel. This results in a loss of generality and uniformity across systems. Based on principles of metamodel-driven system development, we have implemented a platform that can support various categories of hypermedia systems through the generality and extensibility of the metamodel. We present our metamodel and show how it generalises concepts present in a range of hypermedia and link server systems.

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With the emergence of digital pen and paper interfaces, there is a need for gesture recognition tools for digital pen input. While there exists a variety of gesture recognition frameworks, none of them addresses the issues of supporting application developers as well as the designers of new recognition algorithms and, at the same time, can be integrated with new forms of input devices such as digital pens. We introduce iGesture, a Java-based gesture recognition framework focusing on extensibility and cross-application reusability by providing an integrated solution that includes tools for gesture recognition as well as the creation and management of gesture sets for the evaluation and optimisation of new or existing gesture recognition algorithms. In addition to traditional screen-based interaction, iGesture provides a digital pen and paper interface.

Combined pen and touch input is an interaction paradigm attracting increasing interest both in the research community and recently in industry. In this paper, we illustrate how pen and touch interaction techniques can be leveraged for editing and authoring of presentational documents on digital tabletops. Our system exploits the rich interactional vocabulary afforded by the simultaneous availability of the two modalities to provide gesture-driven document editing functionality as an expert alternative to widgets. For our bimanual gestures, we make use of non-dominant hand postures to set pen modes in which the dominant hand articulates a variety of transactions. We draw an analogy between such modifier postures and modifier keys on a keyboard to construct command shortcuts. Based on this model, we implement a number of common document editing operations, including several page and element manipulations, shape and text input with styling, clipart retrieval and insertion as well as undo/redo. The results of a lab study provide insights as to the strengths and limitations of our approach.

Context-aware computing is a major trend in mobile computing, pervasive computing and web engineering. Several models, frameworks and infrastructures have been developed to represent, process and manage context. While most of these approaches support the adaptation of application logic based on context, the requirements of context-aware systems in terms of data management have received little attention. This is most apparent in the field of web engineering as many web sites are data-intensive and require context-dependent content adaptation to support internationalisation, personalisation and multiple channels. We present a version model featuring alternative versions for context-aware data management and query processing that has been integrated in an object-oriented database system. Finally, we also describe the implementation of a mobile tourist information system based on this system.