Anton Eliëns

Patterns as Tools for User Interface Design

Designing usable systems is difficult and designers need effective tools that are usable themselves. Effective design tools should be based on proven knowledge of design. Capturing knowledge about the successful design of usable systems is important for both novice and experienced designers and traditionally, this knowledge has largely been described in guidelines. However, guidelines have shown to have problems concerning selection, validity and applicability. Patterns have emerged as a possible solution to some of the problems from which guidelines suffer. Patterns focus on the context of a problem and solution thereby guiding the designer in using the design knowledge. Patterns for architecture or software engineering are not identical in structure and user interface design also requires its own structure for patterns, focusing on usability. This paper explores how patterns for user interface design must be structured in order to be effective and usable tools for designers. A structure for user interface design patterns is proposed and is illustrated with an example.

STEP: a Scripting Language for Embodied Agents

In this chapter we propose a scripting language, called STEP, for embodied agents, in particular for their communicative acts like gestures and postures. Based on the formal semantics of dynamic logic, STEP has a solid semantic foundation, in spite of a rich number of variants of the compositional operators and interaction facilities on worlds. STEP has been implemented in the distributed logic programming language DLP, a tool for the implementation of 3D web agents. In this chapter, we discuss principles of scripting language design for embodied agents and several aspects of the application of STEP.

Implementation of a scripting language for VRML/X3D-based embodied agents

Embodied agents or humanoid avatars may effectively be used to communicate with human users. Currently there is a wide range of specification formalisms and scripting languages for embodied agents, many of which are of a somewhat ad hoc nature lacking clear semantics. In this paper, we discuss the implementation of a scripting language for humanoid avatars in VRML/X3D-based environments. The scripting language STEP is based on dynamic logic, which provides a clear semantics for complex behavioral patterns. Moreover, the implementation of STEP is realized in a platform that extends VRML/X3D with distributed logic programming (DLP), which provides the computational support necessary to realize such complex behavioral patterns as well as the interaction with a (rich media) 3D environment. As an application example, we will discuss the development of an instructional VR for Tai Chi (the Chinese art of movement), illustrating how our approach allows for the creation of reusable libraries of behavioral patterns. We will discuss some implementation issues, in particular how to realize parallel actions and synchronization within an environment.

Navigation by query in virtual worlds

Web-based 3D virtual environments suffer from the classic problem of users getting ’lost-in-cyberspace’. Apart from getting lost, it is hard for an average user to discover all that a specific world has to offer without spending considerable time exploring that world. In order to remedy this situation we propose navigation by query. The user interface for 3D virtual environments usually allows users to ’walk’ around in the virtual world. Navigation by query augments this interface by allowing users to navigate a virtual world by means of querying its content. We present the concept of navigation by query and discuss the requirements for an implementation for a VRML based environment. Additionally we illustrate problems an implementation must solve by presenting a prototype implementation.

3D agent-based virtual communities

In this paper we propose an approach to 3D agent-based virtual communities in which autonomous agents are participants in VRML-based virtual worlds to enhance the interaction with users or serve as intelligent navigation assistants. In addition, an agent communication language (ACL) is designed as a high-level communication facility, in particular for the realization of shared objects in virtual communities. As a typical example of 3D agent-based virtual communities, a VRML-based multi-user soccer game has been developed and implemented in the distributed logic programming language DLP. We discuss how DLP can be used for the implementation of 3D agent-based virtual communities.

Integrating applications and the World-Wide Web

Abstract This paper describes how to integrate the World-Wide Web (WWW) with applications. By means of the web widget, which is part of Hush, the WWW is made available to Tcl/Tk/Hush programmers. Apart from using WWW as part of an application, it also allows one to embed scripts into a web page. This results in a mutual integration of applications and the WWW. Both forms of integration will be described. Some new possibilities of embedded scripts such as inline MPEG, interactive games and navigation facilities will be discussed.

A taxonomy of web agents

We propose a taxonomy of Web agents, which encompasses agents that provide a text-based interface to, for example, information retrieval services as well as avatar-embodied guides that help visitors to navigate in virtual environments. Our taxonomy must be regarded as an instrument to delineate targets for research and the realization of prototype applications that demonstrate the usefulness of agent-based intelligence on the Web. In addition, we deploy our agent-taxonomy to establish the implications particular target applications have with respect to software architecture and computational resources.

Jamming (on) the Web

Abstract The Web has become a dominant medium for the dissemination of information and, more recently, for collaborative work as well. The focus has been mainly on textual and graphical information, hardly addressing topics related to musical information. We present a framework that makes musical works accessible for Web users by offering high level support for the display of musical material on the Web as well as for live jam sessions. Our framework consists of a browser plug-in that supports the display and editing of scores as well as playing scores by connecting to a shared MIDI server. To participate in a jam session, clients of the MIDI server can also send data in real time, for instance by using a keyboard embedded in a Web page. We discuss the issues involved in displaying musical material on the Web and we sketch the technical architecture of our framework.

Style sheet support for hypermedia documents

Hypermedia documents are most often created with a particular presentation environment in mind. This requires the authoring of one document per presentation platform. As pointed out in [], much implementation effort can be avoided by specifying how the same underlying document can be presented in different environments. A style sheet defines a mapping from a source document to a presentation for it. We discuss the existing use of style sheets as applied to text and discuss their application to the case of hypermedia, and in particular how they need to be extended.

XSTEP: a markup language for embodied agents

In this paper we propose an XML-based markup language. called XSTEP for embodied agents, based on the scripting language STEP. XSTEP is the XML-based successor of STEP. The scripting language STEP incorporates the formal semantics of dynamic logic, and has been implemented in the distributed logic programming language DLP, a tool for the implementation of 3D Web agents. In this paper we discuss the issues of markup language design for embodied agents and several aspects of the implementation and application of XSTEP.