607902
A Framework for Handling Inconsistency in Changing Ontologies
One of the major problems of large scale, distributed and evolving ontologies is the potential introduction of inconsistencies. In this paper we survey four different approaches to handling inconsistency in DL-based ontologies: consistent ontology evolution, repairing inconsistencies, reasoning in the presence of inconsistencies and multi-version reasoning. We present a common formal basis for all of them, and use this common basis to compare these approaches. We discuss the different requirements for each of these methods, the conditions under which each of them is applicable, the knowledge requirements of the various methods, and the different usage scenarios to which they would apply.
11486065
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.
171830
Inconsistencies, Negations and Changes in Ontologies
Ontology management and maintenance are considered cornerstone issues in current Semantic Web applications in which semantic integration and ontological reasoning play a fundamental role. The ability to deal with inconsistency and to accommodate change is of utmost importance in real-world applications of ontological reasoning and management, wherein the need for expressing negated assertions also arises naturally. For this purpose, precise, formal definitions of the the different types of inconsistency and negation in ontologies are required. Unfortunately, ontology languages based on Description Logics (DLs) do not provide enough expressive power to represent axiom negations. Furthermore, there is no single, well-accepted notion of inconsistency and negation in the Semantic Web community, due to the lack of a common and solid foundational framework. In this paper, we propose a general framework accounting for inconsistency, negation and change in ontologies. Different levels of negation and inconsistency in DL-based ontologies are distinguished. We demonstrate how this framework can provide a foundation for reasoning with and management of dynamic ontologies.
18313204
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.
14014109
Dynamic Goal Hierarchies
In this paper we introduce and formalise dynamic goal hierarchies. We begin with a formal definition of goals, according to which they are rational desires. In particular, we require that an agent's goals are coherent; that is, that the agent believes that each goal is jointly realisable with all of the goals which the agent considers to be more important. Thus an agent's goals form a hierarchy, and new goals are defined with reference to it. We then show how preferential entailment can be used to formalise the rational revision of goals and goal hierarchies.
1948717
Reusable Gestures for Interactive Web Agents
In this paper we present an approach to define reusable gestures for embodied web agents, given according to the H-anim standard for VRML. We identify the dimensions to compare gestures and criteria to circumscribe a set of gestures an avatar should be endowed with. Based on these dimensions and criteria, we propose a uniform way to define a wide range of gestures that may be adapted to particular circumstances and personal style. We have implemented our gesture library in STEP, which is a scripting language for humanoids based on dynamic logic. We will discuss the example of conducting music, to explain our approach to the parameterized definition and control of gestures. We conclude by briefly discussing issues for future research.
8291104
An enhanced framework for real-time hair animation
Maximizing visual effect is a major problem in real-time animation. A real-time hair animation framework was proposed previously by C. K. Koh and Z. Huang (2000, 2001) based on 2D representation and texture mapping. One problem is that it lacks of the volumetric effect due to its 2D nature. This paper presents a technique using the U-shape strip to solve the problem.
17908385
The hierarchical degree-of-visibility tree
In this paper, we present a novel structure called the hierarchical degree-of-visibility tree (HDoV-tree) for visibility query processing in visualization systems. The HDoV-tree builds on and extends the R-tree such that 1) the search space is pruned based on the degree of visibility of objects and 2) internal nodes store level-of-details (LoDs) that represent a collection of objects in a coarser form. We propose two tree traversal algorithms that balance performance and visual fidelity, explore three storage structures for the HDoV-tree, and develop novel caching techniques for disk-based HDoV-tree. We implemented the HDoV-tree in a prototype walkthrough system called VISUAL. Our experimental study shows that VISUAL can lead to high frame rates without compromising visual fidelity.
1637377
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.
14317741
Interactive 3D modeling using only one image
For virtual reality systems, modeling of 3D objects and scenes is important and challenging. In this paper, we present an image-based interactive 3D modeling framework consisting of three major modules: photogrammetric modeling, human interaction, and texture mapping. These three modules are not sequentially used and they are mixed in the whole modeling process. The major idea is to explore the use of images in interactive modeling systems to achieve the automation. In particular, the use of only one image is addressed. On one side, unlike the common fully interactive modeling framework, the users are not required to specify some low level details interactively which can be derived automatically from the image. On the other side, it still requires human interactions to do some high level tasks that the algorithms are difficult to perform automatically. We have implemented the framework and experimental results are good.
1065063
Using A-buffer in radiosity
Anti-aliasing in form factor computation and precise determination of shadow boundaries are important issues for radiosity method. A-buffer is a technique introduced by L. Carpenter (1984) for anti-aliasing in hidden surface removal. In this paper, we propose a method based on the A-buffer to replace the Z-buffer in the computation of form factors using the Hemicube for anti-aliasing. The method directly computes shadow boundaries in contrast to the adaptive re-meshing approach. Though the processing of shadow boundaries is not fast, only one discontinuity meshing (no iteration) is required. We implement the method in an infrastructure building design system.