Christopher Wolfe

Fiia: user-centered development of adaptive groupware systems

Adaptive groupware systems support changes in users locations, devices, roles and collaborative structure. Developing such systems is difficult due to the complex distributed systems programming involved. In this paper, we introduce Fiia, a novel architectural style for groupware. Fiia is user-centered, in that it allows easy specification of groupware structured around users settings, devices and applications, and where adaptations are specified at a high level similar to scenarios. The Fiia.Net toolkit automatically maps Fiia architectures to a wide range of possible distributed systems, under control of an annotation language. Together, these allow developers to work at a high level, while retaining control over distribution choices.

Gone but not forgotten: designing for disconnection in synchronous groupware

Synchronous groupware depends on the assumption that people are fully connected to the others in the group, but there are many situations (network delay, network outage, or explicit departure) where users are disconnected for various periods. There is little research dealing with disconnection in synchronous groupware from a user and application perspective; as a result, most current groupware systems do not handle disconnection events well, and several user-level problems occur. To address this limitation, we developed the Disco framework, a model for handling several types of disconnection in synchronous groupware. The framework considers how disconnections are identified, what senders and receivers should do during an absence, and what should be done with accumulated data upon reconnection. We have implemented the framework in three applications that show the feasibility, generality, and functionality of our ideas. Our framework is the first to deal with a full range of disconnection issues for synchronous groupware, and shows how groupware can better support the realities of distributed collaboration.

A low-cost infrastructure for tabletop games

Tabletop games provide an intimate gaming experience where groups of friends can interact in a shared space using shared physical props. Digital tabletop games show great promise in bringing this experience to video game players. However the cost of developing tabletop games is high due to the need for expensive hardware and complex software. In this paper, we introduce EquisFTIR, a low-cost hardware and software infrastructure for digital tabletop gaming. We illustrate the infrastructure through Asterocks, a novel tabletop game.

Plug-replaceable consistency maintenance for multiplayer games

Consistency maintenance of replicated data in multiplayer games is a challenging issue due to the performance constraints of real-time interactive applications. We present an approach which separates game logic from consistency maintenance code through the use of reusable, plug-replaceable concurrency control and consistency maintenance (CCCM) modules. Using plug-replaceable consistency maintenance strategies also permits rapid comparisons of multiple approaches, which facilitates experimentation. We conduct a case study to illustrate how multiple consistency maintenance strategies can be applied without changing the original game code.

Seeing through the fog: an algorithm for fast and accurate touch detection in optical tabletop surfaces

Fast and accurate touch detection is critical to the usability of multi-touch tabletops. In optical tabletops, such as those using the popular FTIR and DI technologies, this requires efficient and effective noise reduction to enhance touches in the cameras input. Common approaches to noise reduction do not scale to larger tables, leaving designers with a choice between accuracy problems and expensive hardware. In this paper, we present a novel noise reduction algorithm that provides better touch recognition than current alternatives, particularly in noisy environments, without imposing higher computational cost. We empirically compare our algorithm to other noise reduction approaches using data collected from tabletops at research labs in Canada and Europe.

An Incremental Algorithm for High-Performance Runtime Model Consistency

We present a novel technique for applying two-level runtime models to distributed systems. Our approach uses graph rewriting rules to transform a high-level source model into one of many possible target models. When either model is changed at runtime, the transformation is incrementally updated. We describe the theory underlying our approach, and show restrictions sufficient for a simple and efficient implementation. We demonstrate this implementation in Fiia.Net , our model-based toolkit for developing adaptive groupware. Developers using Fiia.Net control components and connections through a high-level conceptual runtime model. Meanwhile, the toolkit transparently maintains the underlying distributed system, and propagates failures back into the conceptual model. This approach provides high stability, and performance that is sufficiently fast for interactive applications.

Visual constraint diagrams: runtime conformance checking of UML object models versus implementations

This paper presents visual constraint diagrams (VCD), an extension to UML (Unified Modeling Language) object diagrams for expressing constraints over object models. VCD allows designers to express well-formedness constraints that cannot be expressed using class diagrams alone; an example of such a constraint is that a linked list data structure cannot have any loops. VCD offers two advances over existing techniques: (1) they allow constraints to be expressed within the visual notation of UML, without resorting to complex textual notations such as OCL; and (2) VCD can be checked at runtime, increasing the value of design documents to developers. An editor and a checker for VCD have been implemented as part of the Rosetta software design tool.

Fiia: A Model-Based Approach to Engineering Collaborative Augmented Reality

Augmented reality systems often involve collaboration among groups of people. While there are numerous toolkits that aid the development of such augmented reality groupware systems (e.g., ARToolkit and Groupkit), there remains an enormous gap between the specification of an AR groupware application and its implementation. In this chapter, we present Fiia, a toolkit which simplifies the development of collaborative AR applications. Developers specify the structure of their applications using the Fiia modeling language, which abstracts details of networking and provides high-level support for specifying adapters between the physical and virtual world. The Fiia.Net runtime system then maps this conceptual model to a runtime implementation. We illustrate Fiia via Raptor, an augmented reality application used to help small groups collaboratively prototype video games.

Scenarchitectures: the use of domain-specific architectures to bridge design and implementation

In this paper, we present scenarchitectures, a means of raising the level of design of advanced interactive systems. Scenarchitectures combine elements of scenarios and system architectures, and can be used during the user interface design process as an adjunct to other design tools such as textual scenarios and story boards. Meanwhile, scenarchitectures can be automatically transformed to system architectures, providing a link between design and implementation. Using two existing scenarchitectural notations, we investigate the role of scenarchitectures in the design process. We then show how model-transformation techniques can be used to automatically derive system architectures from scenarchitectures, and conclude with concrete examples of the application of the scenarchitectural approach to the design of a mixed-reality system.