George Anastassakis

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.

Behavior believability in virtual worlds: agents acting when they need to

Believability has been a perennial goal for the intelligent virtual agent community. One important aspect of believability largely consists in demonstrating autonomous behavior, consistent with the agent’s personality and motivational state, as well as the world conditions. Autonomy, on behalf of the agent, implies the existence of an internal structure and mechanism that allows the agent to have its own needs and interests, based on which the agent will dynamically select and generate goals that will in turn lead to self-determined behavior. Intrinsic motivation allows the agent to function and demonstrate behavior, even when no external stimulus is present, due to the constant change of its internal emotional and physiological state. The concept of motivation has already been investigated by research works on intelligent agents, trying to achieve autonomy. The current work presents an architecture and model to represent and manage internal driving factors in intelligent virtual agents, using the concept of motivations. Based on Maslow and Alderfer’s bio-psychological needs theories, we present a motivational approach to represent human needs and produce emergent behavior through motivation synthesis. Particular attention is given to basic, physiological level needs, which are the basis of behavior and can produce tendency to action even when there is no other interaction with the environment.

A Platform for Teaching Logic Programming Using Virtual Worlds

Logic Programming (LP) is an essential part of many academic curricula and it is extensively employed in the field of Artificial Intelligence. However, being based on a fundamentally different paradigm and lacking any visual tools for inexperienced users, its teaching may lead to confusion and low student motivation. Virtual Worlds (VWs) may help overcome these obstacles, as they have been successfully used in computer programming education. In this paper we present the MeLoISE platform (Meaningful Logical Interpretations of Simulated Environments) for teaching LP in VWs, through which students can experience a collaborative visual interface to the Prolog programming language. We also present an evaluation of MeLoISE, which was conducted during a learning activity that engaged students in collaborative programming for 2 problem scenarios. Students performed very well and were enthusiastic with the new environment.

A Transparent and Decentralized Model of Perception and Action for Intelligent Virtual Agents

Intelligent virtual agent behaviour is a crucial element of any virtual environment application as it essentially brings the environment to life, introduces believability and realism and enables complex interactions and evolution over time. However, the development of mechanisms for virtual agent perception and action is neither a trivial nor a straight-forward task. In this paper we present a model of perception and action for intelligent virtual agents that meets specific requirements and can as such be systematically implemented, can seamlessly and transparently integrate with knowledge representation and intelligent reasoning mechanisms, is highly independent of virtual world implementation specifics, and enables virtual agent portability and reuse.

A SYSTEM FOR LOGIC-BASED INTELLIGENT VIRTUAL AGENTS

Combination of logic-based artificial intelligence with virtual reality in intelligent agent systems is an approach not extensively sought after to date. It is our belief that significant gain is to be expected if the technical challenges involved are overcome. In this paper, we describe the mVlTAL intelligent agent system, which is our latest effort towards this direction. The system is a contemporary intelligent agent system with applications in numerous areas, including intelligent virtual environments and formal artificial intelligence research. The system focuses largely on logic-based approaches, which are present in almost every aspect of it, including modeling, knowledge representation, definition of agent behaviors and inter-agent communication. In addition, virtual manifestation of the world and agents is also an inherent characteristic of the system. The system, even if still in a development and evaluation stage, has already been employed in experimental and educational applications, demonstrating the potential benefits of such an approach.

Modelling basic needs as agent motivations

Any autonomous agent behaviour generation mechanism should incorporate as a core module, a source of internal motivation that functions as a start point for agent behaviour to commence. Intelligent virtual agents are typically respondent to external stimuli, however, their behaviour becomes repetitive and trivial when these stimuli are missing. We argue that it is necessary for virtual agents to be equipped with intrinsic motivations that energise and direct their behaviour, in order to function in a coherent and believable way. Adopting the general principles of hierarchical motivation theories, in the current work, we attempt to model physiological needs as the lowest and basic level of motivations, in a layered motivational architecture. Based on readings from physiology, we present the mechanisms underlying the function of four basic needs and propose a model that allows the incorporation of plausible human-like needs in an intelligent virtual agent.

A framework for uniform development of intelligent virtual agents

As the field of Intelligent Virtual Agents evolves and advances, an ever increasing number of functional and useful applications are presented. Intelligent Virtual Agents have become more realistic, intelligent and sociable, with apparent and substantial benefits to domains such as training, tutoring, simulation and entertainment. However, even though many end-users can enjoy these benefits today, the development of such applications is restricted to specialized research groups and companies. Obvious and difficult-to-overcome factors contribute to this. The inherent complexity of such applications results in increased theoretical and technical requirements to their development. Furthermore, Intelligent Virtual Agent systems today typically offer ad hoc, if any, design and development means that lack completeness and a general-purpose character. Significant efforts have been successfully made towards deriving globally accepted standards; nevertheless these mostly focus on communication between heterogeneous systems and not on design and development. In this paper, we present our current efforts towards a novel architecture for Intelligent Virtual Agents which is based on our previous work in the field and encompasses the full range of characteristics considered today as fundamental to achieving believable Intelligent Virtual Agent behaviour. In the spirit of enabling and easing application design and development, as well as facilitating further research, our architecture is tightly coupled with a behaviour specification language that uniformly covers all aspects and stages of the development process. We also present the key guidelines for a minimal but functional implementation, aimed in validation and experimentation.

Teaching and learning logic programming in virtual worlds using interactive microworld representations

Abstract: Logic Programming (LP) follows the declarative programming paradigm, which novice students often find hard to grasp. The limited availability of visual teaching aids for LP can lead to low motivation for learning. In this paper, we present a platform for teaching and learning Prolog in Virtual Worlds, which enables the visual interpretation and verification of program results in a straightforward fashion and requires students to adopt a collaborative problem‐solving approach. The results of the pilot application and student‐centered evaluation of the platform are encouraging regarding group learning performance and user experience. The paper contributes to current practice of teaching and learning LP by proposing a metaphor and a system that can empower the educational process with toy world examples visualized in a shared 3D environment. [ABSTRACT FROM AUTHOR]

A tool for programming the behaviour of intelligent virtual agents in Prolog

The definition of intelligent virtual agent behaviour is a key stage in the process of developing any intelligent virtual environment application. Ranging from simple scripting languages to full-featured, general-purpose programming languages, the means available to developers for defining agent behaviour are bound by the choice of development methodology and platform for the entire system. In this paper, we present a tool for programming the behaviour of intelligent virtual agents in intelligent virtual environment applications on an implementation-independent basis using the Prolog language. Our aim is to evaluate the potential of Prolog as a means for defining intelligent virtual agent behaviour as well as extend our previous work in the field.

Towards a Methodology for Integrating Physics Engines with Virtual Environments: A Case Study Using the REVE Platform and the Vesper3D Physics Engine

Virtual environments are used today in a variety of application areas to produce virtual worlds that are highly dynamic, not only as a result of autonomous agent behaviour but, also, due to the effects of the application of physics laws. Motivated by the inherent complexity in both virtual environment systems and physics engines, we present our efforts so far towards a methodology for the systematic and uniform integration of physics engines with virtual environments by discussing the integration of the Vesper3D physics engine with the REVE platform for intelligent virtual environments.