Themis Panayiotopoulos

Hermes – a framework for location-based data management

The aim of this paper is to demonstrate Hermes, a robust framework capable of aiding a spatio-temporal database developer in modeling, constructing and querying a database with dynamic objects that change location, shape and size, either discretely or continuously in time. Hermes provides spatio-temporal functionality to state-of-the-art Object-Relational DBMS (ORDBMS). The prototype has been designed as an extension of STAU [6], which provides data management infrastructure for historical moving objects, so as to additionally support the demands of real time dynamic applications (e.g. Location-Based Services – LBS). The produced type system is packaged and provided as a data cartridge using the extensibility interface of Oracle10g. The offspring of the above framework extends PL/SQL with spatio-temporal semantics. The serviceableness of the resulting query language is demonstrated by realizing queries that have been proposed in [9] as a benchmarking framework for the evaluation of LBS.

SimHuman: A Platform for Real-Time Virtual Agents with Planning Capabilities

In this paper, we present SimHuman, a platform for the generation of real-time 3D environments with virtual agents. SimHuman is highly dynamic and configurable, as it is not based on fixed scenes and models, and has an embedded physically based modelling engine. Its agents can use features such as path finding, inverse kinematics and planning to achieve their goals. The paper explains in detail design and implementation issues and presents the architecture of the system as well as an illustrative example.

Multi-agent Systems as Intelligent Virtual Environments

Intelligent agent systems have been the subject of intensive research over the past few years; they comprise one of the most promising computing approaches ever, able to address issues that require abstract modelling and higher level reasoning. Virtual environments, on the other hand, offer the ideal means to produce simulations of the real world for purposes of entertainment, education, and others. The merging of these two fields seems to have a lot to offer to both research and applications, if progress is made on a co-ordinated manner and towards standardization. This paper is a presentation of VITAL, an intelligent multi-agent system able to support general-purpose intelligent virtual environment applications.

A platform for virtual museums with personalized content

Presentation of content is an important aspect of today’s virtual reality applications, especially in domains such as virtual museums. The large amount and variety of exhibits in such applications raise a need for adaptation and personalization of the environment. This paper presents a content personalization platform for Virtual Museums, which is based on a semantic description of content and on information implicitly collected about the users through their interactions with the museum. The proposed platform uses stereotypes to initialize user models, adapts user profiles dynamically and clusters users into similar interest groups. A science fiction museum has been set up as a case study for this platform and an evaluation has been carried out.

Virtual Agent Societies with the mVITAL Intelligent Agent System

Intelligent multi-agent systems are currently used for a variety of purposes, both in research and for real-world applications. One of their most interesting, yet not fully explored uses, is as frameworks to support computer-based simulations of virtual worlds inhabited by life-like entities, that is, intelligent virtual environments, for purposes of education, demonstration and entertainment. This paper is a presentation of mVITAL, an intelligent multi-agent system aiming to serve most of the fields such systems are today used in, while being fully capable of supporting intelligent virtual environment applications, where issues such as sophisticated virtual reality representation, advanced reasoning, as well as user embodiment, intervention and interaction, are crucial. To justify this, a fully operational example of such an application, namely, the Vital Playground, is also presented.

Intelligent Guidance in a Virtual University

Virtual Reality technology [1–3], has introduced a new spatial metaphor with very interesting applications on Intelligent Navigation [4], social behaviour over virtual worlds [5], full body interaction [6], virtual studios [7], etc.

A Tool for Constructing 3D Environments with Virtual Agents

The use of Virtual Environments as a user interface is essential for certain types of applications, both in education and entertainment. These worlds are even more attractive for the user when they are neither static nor pre-scripted, but have dynamic characteristics and are populated by autonomous entities, also called virtual agents. There has been a lot of research concerning visualization, animation and behavior of virtual agents, but there are no generic architectures, methodologies and tools for the development of intelligent virtual environments, i.e. 3D environments with autonomous virtual agents. In this paper, we present SimHuman, a tool for the construction of virtual worlds with autonomous entities, targeted for a specific group of applications, such as simple simulation systems, virtual environments, educational applications, multimedia presentations, etc. It consists of a programming library and two utilities and it is highly dynamic and configurable, as it is not based on fixed scenes and models. It has embedded characteristics such as Inverse Kinematics, Physically Based Modeling, Collision Detection and Response, and Vision. SimHuman incorporates some important features for designing and building virtual environments and turns out to be an effective tool for interactive 3D applications with virtual agents.

Branching-time logic programming: the language Cactus and its applications

Temporal programming languages provide a powerful means for the description and implementation of dynamic systems. However, most temporal languages are based on linear time, a fact that renders them unsuitable for certain types of applications (such as expressing properties of non-deterministic programs). In this paper we introduce the new temporal logic programming language Cactus, which is based on a branching notion of time. In Cactus, the truth value of a predicate depends on a hidden time parameter which varies over a tree-like structure. As a result, Cactus can be used to express in a natural way non-deterministic computations or generally algorithms that involve the manipulation of tree data structures. Moreover, Cactus appears to be appropriate as the target language for compilers or program transformers. Cactus programs can be executed using BSLD-resolution, a proof procedure based on the notion of canonical temporal atoms/clauses.

An Intelligent Agent Framework in VRML Worlds

Agent-based technologies have been rapidly emerging since the beginning of the 1990s [1–5]. J.P. Muller, [4], states that ‘Agents are autonomous or semi-autonomous hardware or software systems that perform tasks in complex, dynamically changing environments’. This means that Intelligent Agents observe the environment, maintain an internal representation of the world, make decisions and perform tasks (executing actions).

Distributed Virtual Reality Authoring Interfaces for the WWW: The VR-Shop Case

Electronic commerce is emerging as an important domain of integration and enhancement of more specific technologies and research efforts. It is clear that the role of WWW in this context is a cornerstone as the medium of information dissemination. A trend in e-commerce is to provide to the potential customers the ability to view and “try” the products in a persuasive 3D representation. We have designed and implemented a system for WWW enabled interactive design & visualization of a room, definition of pieces of furniture and placement of domestic appliances. The system conveys a generic approach for distributed creation and update of virtual worlds as means of interaction and information dissemination in an e-commerce context.