Peter Ørbæk

Towards geo-spatial hypermedia: Concepts and prototype implementation

This paper combines spatial hypermedia with techniques from Geographical Information Systems and location based services. We describe the Topos 3D Spatial Hypermedia system and how it has been developed to support geo-spatial hypermedia coupling hypermedia information to model representations of real world buildings and landscapes. The prototype experiments are primarily aimed at supporting architects and landscape architects in their work on site. Here it is useful to be able to superimpose and add different layers of information to, e.g. a landscape depending on the task being worked on. We introduce a number of central concepts to understand the relation between hypermedia and spatial information management. The distinction between metaphorical (and abstract) versus literal (and concrete) spaces is introduced together with a workspace composition semantics and a distinction between direct and indirect navigation. Finally, we conclude with a number of research issues which are central to the future development of geo-spatial hypermedia, including design issues in combining metaphorical and literal hypermedia space, as well as a discussion of the role of spatial parsing in a geo-spatial context.

Physical hypermedia: organising collections of mixed physical and digital material

This paper addresses the problem of organizing material in mixed digital and physical environments. It presents empirical examples of how people use collectional artefacts and organize physical material such as paper, samples, models, mock-ups, plans, etc. in the real world. Based on this material, we propose concepts for collectional actions and meta-data actions, and present prototypes combining principles from augmented reality and hypermedia to support organising and managing mixtures of digital and physical materials. The prototype of the tagging system is running on digital desks and walls utilizing Radio Frequency IDentifier (RFID) tags and tag-readers. It allows users to tag important physical materials, and have these tracked by antennas that may become pervasive in our work environments. We work with three categories of tags: simple object tags, collectional tags, and tooltags invoking operations such as grouping and linking of physical material. Our primary application domain is architecture and design, thus we discuss use of augmented collectional artefacts primarily for this domain.

Collaborative augmented reality environments: integrating VR, working materials, and distributed work spaces

In this work, we present a new method for displaying stereo scenes, which speeds up the rendering time of complex geometry. We first discuss a scene splitting strategy, allowing us to partition objects to the distant background or the near foreground. Furthermore, wededuce a computation rule for positioning a cutting plane in the scene.

Physical hypermedia: augmenting physical material with hypermedia structures

This paper introduces the notion of physical hypermedia, addressing the problem of organizing material in mixed digital and physical environments. Based on empirical studies, we propose concepts for collectional actions and meta-data actions, and present prototypes combining principles from augmented reality and hypermedia to support organization of mixtures of digital and physical materials. Our prototype of a physical hypermedia system is running on an augmented architects desk and digital walls utilizing Radio Frequency Identifier (RFID) tags as well as visual tags tracked by cameras. It allows users to tag physical materials, and have these tracked by readers (antennas) that may become pervasive in our work environments. In the physical hypermedia system, we work with three categories of RFID tags: simple object tags, collectional tags, and tooltags invoking operations such as grouping and linking of physical material. In addition, we utilize visual ARToolKit tags for linking and navigating 3D models on a physical desk. Our primary application domain is architecture and design, and so we discuss the use of augmented collectional artifacts primarily for this domain.

OASIS: An Optimizing Action-Based Compiler Generator

Action Semantics is a new and interesting foundation for semantics based compiler generation. In this paper we present several analyses of actions, and apply them in a compiler generator capable of generating efficient, optimizing compilers for procedural and functional languages with higher order recursive functions. The automatically generated compilers produce code that is comparable with code produced by handwritten compilers.

An experimental system for distributed classroom education

Abstract This paper describes an experimental system for classroom-based tele-education based on IP multicast. It gives an overview of the system and describes how the system is designed to avoid a single central point of failure. The system supports locally controlled video mixing, provides simple floor arbitration without a central controller, and finally implements a new wavelet-based video compression scheme to achieve better video quality for large screen projection. The new network protocols involved are briefly described.

Polyvariant specialisation for higher-order, block-structured languages

We propose a simple method for polyvariant specialisation of higher-order programs in a way that preserves block structure. The method is based on identifying the log (the ‘(seenbefore” list ) as a derivative of the procedure environment. Most contemporary partial evaluators use polyvariant specialisation. Due to scoping problems with the definitions introduced by the partial evaluator, this algorithm cannot preserve blocks in the presence of higher-order values. (The problem is related to the so-called “upwards funarg” problem of Lisp.) Instead, the source program is “lambda-lifted” (transformed into recursive equations) to remove local scope before specialisation — scoping problems are evaded rather than solved. Lambda-lifting, however, destroys any locality of variables that might be used in compiling the residual program. Also, the residual program becomes unreadable to the user, complicating both binding-time improvement and binding-time debugging. This paper re-expresses the polyvariant specialisation algorithm by deriving the log from the environment of an ordinary interpreter, and solves the problem of retaining block structure based on this analogy. The resulting algorithm extends polyvariant specialisation to handle blocks and higherorder values in the natural way. We give the algorithm for an offline specialiser. We have also implemented the algorithm in the online partial evaluator POPE and the preliminary experimental results show significant speedup for many block-structured residual programs compared to their lambda-lift ed counterparts.

Finding hyper-structure in space: spatial parsing in 3D

Abstract Spatial parsers augment spatial hypermedia systems by letting the computer perceive the informal -but visually apparent - groupings formed by humans working with a spatial hypermedia tool. A number of research systems implementing 2D spatial parsing have been described in recent years. This paper extends spatial parsing to 3D and describes an implementation of a tailorable 3D spatial parser for the Topos system: a 3D information organization tool for use on desktops, interactive whiteboards and tables. The parser maintains a proximity graph of the heterogeneous 3D objects and applies structure experts and global repression and reinforcement techniques to this graph to find structures. A number of issues pertaining to 3D parsing as opposed to 2D parsing are discussed. The paper also presents a simple and efficient 2D parser for 3D scenes and compares it to the true 3D parser.

Spatial computing and spatial practices

The gathering momentum behind the research agendas of pervasive, ubiquitous and ambient computing, set in motion by Mark Weiser (1991), offer dramatic opportunities for information systems design. They raise the possibility of “putting computation where it belongs” by exploding computing power out of conventional machines and interfaces, and embedding it in myriad large and small communicating devices and everyday objects. Exciting though these developments are, however, they remain “just technology” unless they can be successfully married to things that people really need and want to do. In addressing the “disappearing computer” we have, therefore, carried over from previous research an interdisciplinary perspective, and a focus on the sociality of action (Suchman 1987).