Themis Panayiotopoulos | University of Piraeus (original) (raw)

Papers by Themis Panayiotopoulos

This paper presents a generalised approach for the incorporation of some inexact reasoning models... more This paper presents a generalised approach for the incorporation of some inexact reasoning models in propositional and first order predicate logic. Incorporated in the proving mechanism is an extended resolution principle. The resolution takes place between geneneral clauses with an arbitrary selection for unification among these clauses.

This paper presents a truly declarative Prolog-like language that is based on attribute grammars,... more This paper presents a truly declarative Prolog-like language that is based on attribute grammars, and imposes no restriction on the ordering of the subgoals when writing a logic rule. The method is based on a multipass attribute grammar evaluator combined with an already developed methodology for relating attribute grammars and logic programming.

The Computer Journal, 1992

Information & Software Technology, Nov 1, 1988

Journal of Internet Technology, Jul 1, 2004

Search engines on the Web are valuable tools for searching information according to a user's... more Search engines on the Web are valuable tools for searching information according to a user's interests whether an individual or a software agent. In the present article we describe the design and the operation mode of SpiderServer, a metasearch engine used for the submission of ...

Springer eBooks, 1999

During the last decade, the need of special manipulation of temporal data has become obvious. Mos... more During the last decade, the need of special manipulation of temporal data has become obvious. Most of the real world trivial applications consider storage and manipulation of temporal data as essential. Examples are applications having to do with scheduling, banking, sales, reservations, transportation, patient medical files etc. However, efficient storage and manipulation of temporal data has always been a great challenge and a problem too.

WIT Transactions on Information and Communication Technologies, 1970

Lecture Notes in Networks and Systems, 2017

SCADA systems play a vital role in the efficient operations of the ports’ Critical Infrastructure... more SCADA systems play a vital role in the efficient operations of the ports’ Critical Infrastructures (CIs) and their Maritime Logistics and Supply Chain Services (MLoSC). In this paper we provide a process-centric modeling approach using BPMN 2.0 specification in order to visualize an attack likely to be detected on SCADA systems. The SCADA model serves as a study on how security concepts (e.g. security paths, vulnerabilities, propagation of attacks) can be represented with modeling notations.

Studies in Computational Intelligence, 2016

As business information is getting more and more difficult to manage, business entities are incre... more As business information is getting more and more difficult to manage, business entities are increasingly adopting business process management practices and tools, providing new models and techniques for process-related information management. In parallel, semantic web technologies are emerging, which are capable of providing methodologies and tools to represent and process the semantic content of business processes. Applying semantic web technologies in business process management can enhance process understanding and can facilitate querying for pertinent process information. This chapter discusses the challenges and benefits associated with the coupling of semantic technologies with business process management and describes a methodology for representing the semantic content of the BPMN specification in the form of ontology. Moreover, it explores query mechanisms for conventional and semantics-based querying of business models.

The Computer Journal, 1992

Information and Software Technology, 1990

... SqR,) = [S,,(R,.) .. S*,(R,,) .. S',,(R,,)] (8) where Sk,(R,,). 1 n, stands for ... Ther... more ... SqR,) = [S,,(R,.) .. S*,(R,,) .. S',,(R,,)] (8) where Sk,(R,,). 1 n, stands for ... Therefore, to implement one of these models, just alter these functions according to their formulas in ... 379 14 Buchanan, BG and Shortliffe, EH Ruh,based expert systems AddisonWesley, Reading, MA, USA ...

Lecture notes in computer science, Sep 1, 2005

RefDoc Refdoc est un service / is powered by. ...

Proceedings of the 5th International Conference on Computer Supported Education, 2013

2015 6th International Conference on Information, Intelligence, Systems and Applications (IISA), 2015

The definition of intelligent virtual agent behaviour is a key stage in the process of developing... more 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.

Knowledge Science, Engineering and Management, 2018

In recent digital evolution years, cyber-terrorist activity is increasingly rising all over the w... more In recent digital evolution years, cyber-terrorist activity is increasingly rising all over the world deploying new methods, using advanced technologies and sophisticated weapons. A potential terrorist attack on a large commercial Port could lead to dramatic losses. This work aims to illustrate methods for recognizing cyber-threats and security weaknesses on the ports’ Critical Infrastructures and explores how these issues can be systematically exploited to harm ports and their vicinity. To this end, we follow an asset-centric approach, which employs knowledge representation techniques, to detect vulnerability chains and possible attack-paths on ports’ assets. Considering the results, a realistic coordinated cyber-attack scenario on the application case of the Cruise Vessel Traffic Service is presented to show how cyber-attacks can be realized by terrorists on commercial ports.

2015 6th International Conference on Information, Intelligence, Systems and Applications (IISA), 2015

The rapid evolution of technology in Management Information Systems has enabled easy access to a ... more The rapid evolution of technology in Management Information Systems has enabled easy access to a huge amount of complex and specialized business information. The vast amount of business information has created the need for investigating ways to improve the efficiency and effectiveness of information retrieval techniques for querying business information. Among the different types of business information, information about business processes has been leveraged with dedicated languages, methods and tools. Business Process Management Notation (BPMN) is an international standard for modeling business processes. In this paper, we first develop the appropriate business process models of a complex real-life scenario using BPMN and we then represent process models in the form of an ontology business process model. We, next, query the two models with the same queries: the BPMN model using a query language for object-oriented databases and the semantic model using the SPARQL ontology-based search language. We compare the two query methods, discuss the results and explain the benefits of using semantics-based information retrieval techniques when dealing with business process information.

DESIDOC Journal of Library & Information Technology

Virtual Exhibitions are single- or multi-user realistic 3D representations of artifact collection... more Virtual Exhibitions are single- or multi-user realistic 3D representations of artifact collections, in which visitors navigate, observe the exhibits, learn related information about them presented in various media, and in some cases interact with them. Given that virtual exhibitions have no physical restrictions, they may host a limitless number of exhibits in a very large presentation space. On the other hand studies have shown that visitors have various goals concerning their experience within an exhibition space, they follow different navigation strategies in browsing the exhibits, and they may be interested only in parts of the collection. These differentiations among online users raise a need for adaptation and personalization of the 3D environment and its content. Researchers in Adaptive Hypermedia distinguish between adaptation of content, adaptation of presentation and modality, and adaptation of structure. In the case of Virtual Exhibitions the content can be adapted by dyn...

Lecture Notes in Computer Science, 2003

This paper discusses the use of intelligent planning as a control mechanism for agents situated i... more This paper discusses the use of intelligent planning as a control mechanism for agents situated in a virtual world. Virtual environments require a planning system that is flexible enough to handle situations impossible to predict before execution has started. In order to produce believable results, the planner should also be able to model and handle emotions. Working towards this direction, the authors propose a motivation-driven, continuous hierarchical planner as an appropriate paradigm.

Lecture Notes in Computer Science, 2005

IVAs and Education.- Training Agents: An Architecture for Reusability.- Ask&Answer: An Educat... more IVAs and Education.- Training Agents: An Architecture for Reusability.- Ask&Answer: An Educational Game Where It Pays to Endear Your Capricious Virtual Companion.- Conversational Agents/NLP.- Natural Behavior of a Listening Agent.- Providing Computer Game Characters with Conversational Abilities.- Fight, Flight, or Negotiate: Believable Strategies for Conversing Under Crisis.- Dialog Simulation for Background Characters.- IVA Architectures.- INTERFACE Toolkit: A New Tool for Building IVAs.- Autonomous Virtual Agents Learning a Cognitive Model and Evolving.- Using Real Objects to Communicate with Virtual Characters.- A Software Engineering Approach Combining Rational and Conversational Agents for the Design of Assistance Applications.- Marve: A Prototype Virtual Human Interface Framework for Studying Human-Virtual Human Interaction.- Cognition, Reasoning and Behaviour.- A Knowledge-Based Scenario Framework to Support Intelligent Planning Characters.- CAA: A Context-Sensitive Agent Architecture for Dynamic Virtual Environments.- When Emotion Does Not Mean Loss of Control.- Social Situated Agents in Virtual, Real and Mixed Reality Environments.- Do You See What Eyes See? Implementing Inattentional Blindness.- Social Causality and Responsibility: Modeling and Evaluation.- NonVerbal Communication.- Teaching Virtual Characters How to Use Body Language.- Direction of Attention Perception for Conversation Initiation in Virtual Environments.- A Model of Attention and Interest Using Gaze Behavior.- Where Do They Look? Gaze Behaviors of Multiple Users Interacting with an Embodied Conversational Agent.- Hierarchical Motion Controllers for Real-Time Autonomous Virtual Humans.- Modeling Dynamic Perceptual Attention in Complex Virtual Environments.- Storytelling/Interactive Narrative.- An Objective Character Believability Evaluation Procedure for Multi-agent Story Generation Systems.- Proactive Mediation in Plan-Based Narrative Environments.- FearNot! - An Experiment in Emergent Narrative.- Intelligent Virtual Agents in Collaborative Scenarios.- Social Intelligence.- A Conversational Agent as Museum Guide - Design and Evaluation of a Real-World Application.- Using Ontology to Establish Social Context and Support Social Reasoning.- Integrating Social Skills in Task-Oriented 3D IVA.- Emotions/Affect/Personality.- Emergent Affective and Personality Model.- Judging Laura: Perceived Qualities of a Mediated Human Versus an Embodied Agent.- The Significance of Textures for Affective Interfaces.- Levels of Representation in the Annotation of Emotion for the Specification of Expressivity in ECAs.- Extended Behavior Networks and Agent Personality: Investigating the Design of Character Stereotypes in the Game Unreal Tournament.- Evaluation and Methodology.- Direct Manipulation Like Tools for Designing Intelligent Virtual Agents.- Social Communicative Effects of a Virtual Program Guide.- Maintaining the Identity of Dynamically Embodied Agents.- The Behavior Oriented Design of an Unreal Tournament Character.- MyTutor: A Personal Tutoring Agent.- Poster Session.- Using Facial Expressions Depicting Emotions in a Human-Computer Interface Intended for People with Autism.- A Survey of Computational Emotion Research.- A Study on Generating and Matching Facial Control Point Using Radial Basis Function.- A Platform Independent Architecture for Virtual Characters and Avatars.- GAL: Towards Large Simulations with Tens of Agents.- Virtual Agents in a Simulation of an ISO-Company.- Appraisal for a Character-Based Story-World.- Evolving Emotional Behaviour for Expressive Performance of Music.- A Model of an Embodied Emotional Agent.- Agent Assistance for 3D World Navigation.- NeXuS: Delivering Perceptions to Situated Embodied Agents.- Emotion in Artificial Intelligence and Artificial Life Research: Facing Problems.- A Synthetic Agent for Mentoring Novice Programmers Within a Desktop Computer Environment.- vBroker: Agents Teaching Stock Market.- Emergence of Representational Structures in Virtual Agents.

This paper presents a generalised approach for the incorporation of some inexact reasoning models... more This paper presents a generalised approach for the incorporation of some inexact reasoning models in propositional and first order predicate logic. Incorporated in the proving mechanism is an extended resolution principle. The resolution takes place between geneneral clauses with an arbitrary selection for unification among these clauses.

This paper presents a truly declarative Prolog-like language that is based on attribute grammars,... more This paper presents a truly declarative Prolog-like language that is based on attribute grammars, and imposes no restriction on the ordering of the subgoals when writing a logic rule. The method is based on a multipass attribute grammar evaluator combined with an already developed methodology for relating attribute grammars and logic programming.

The Computer Journal, 1992

Information & Software Technology, Nov 1, 1988

Journal of Internet Technology, Jul 1, 2004

Search engines on the Web are valuable tools for searching information according to a user's... more Search engines on the Web are valuable tools for searching information according to a user's interests whether an individual or a software agent. In the present article we describe the design and the operation mode of SpiderServer, a metasearch engine used for the submission of ...

Springer eBooks, 1999

During the last decade, the need of special manipulation of temporal data has become obvious. Mos... more During the last decade, the need of special manipulation of temporal data has become obvious. Most of the real world trivial applications consider storage and manipulation of temporal data as essential. Examples are applications having to do with scheduling, banking, sales, reservations, transportation, patient medical files etc. However, efficient storage and manipulation of temporal data has always been a great challenge and a problem too.

WIT Transactions on Information and Communication Technologies, 1970

Lecture Notes in Networks and Systems, 2017

SCADA systems play a vital role in the efficient operations of the ports’ Critical Infrastructure... more SCADA systems play a vital role in the efficient operations of the ports’ Critical Infrastructures (CIs) and their Maritime Logistics and Supply Chain Services (MLoSC). In this paper we provide a process-centric modeling approach using BPMN 2.0 specification in order to visualize an attack likely to be detected on SCADA systems. The SCADA model serves as a study on how security concepts (e.g. security paths, vulnerabilities, propagation of attacks) can be represented with modeling notations.

Studies in Computational Intelligence, 2016

As business information is getting more and more difficult to manage, business entities are incre... more As business information is getting more and more difficult to manage, business entities are increasingly adopting business process management practices and tools, providing new models and techniques for process-related information management. In parallel, semantic web technologies are emerging, which are capable of providing methodologies and tools to represent and process the semantic content of business processes. Applying semantic web technologies in business process management can enhance process understanding and can facilitate querying for pertinent process information. This chapter discusses the challenges and benefits associated with the coupling of semantic technologies with business process management and describes a methodology for representing the semantic content of the BPMN specification in the form of ontology. Moreover, it explores query mechanisms for conventional and semantics-based querying of business models.

The Computer Journal, 1992

Information and Software Technology, 1990

... SqR,) = [S,,(R,.) .. S*,(R,,) .. S',,(R,,)] (8) where Sk,(R,,). 1 n, stands for ... Ther... more ... SqR,) = [S,,(R,.) .. S*,(R,,) .. S',,(R,,)] (8) where Sk,(R,,). 1 n, stands for ... Therefore, to implement one of these models, just alter these functions according to their formulas in ... 379 14 Buchanan, BG and Shortliffe, EH Ruh,based expert systems AddisonWesley, Reading, MA, USA ...

Lecture notes in computer science, Sep 1, 2005

RefDoc Refdoc est un service / is powered by. ...

Proceedings of the 5th International Conference on Computer Supported Education, 2013

2015 6th International Conference on Information, Intelligence, Systems and Applications (IISA), 2015

The definition of intelligent virtual agent behaviour is a key stage in the process of developing... more 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.

Knowledge Science, Engineering and Management, 2018

In recent digital evolution years, cyber-terrorist activity is increasingly rising all over the w... more In recent digital evolution years, cyber-terrorist activity is increasingly rising all over the world deploying new methods, using advanced technologies and sophisticated weapons. A potential terrorist attack on a large commercial Port could lead to dramatic losses. This work aims to illustrate methods for recognizing cyber-threats and security weaknesses on the ports’ Critical Infrastructures and explores how these issues can be systematically exploited to harm ports and their vicinity. To this end, we follow an asset-centric approach, which employs knowledge representation techniques, to detect vulnerability chains and possible attack-paths on ports’ assets. Considering the results, a realistic coordinated cyber-attack scenario on the application case of the Cruise Vessel Traffic Service is presented to show how cyber-attacks can be realized by terrorists on commercial ports.

2015 6th International Conference on Information, Intelligence, Systems and Applications (IISA), 2015

The rapid evolution of technology in Management Information Systems has enabled easy access to a ... more The rapid evolution of technology in Management Information Systems has enabled easy access to a huge amount of complex and specialized business information. The vast amount of business information has created the need for investigating ways to improve the efficiency and effectiveness of information retrieval techniques for querying business information. Among the different types of business information, information about business processes has been leveraged with dedicated languages, methods and tools. Business Process Management Notation (BPMN) is an international standard for modeling business processes. In this paper, we first develop the appropriate business process models of a complex real-life scenario using BPMN and we then represent process models in the form of an ontology business process model. We, next, query the two models with the same queries: the BPMN model using a query language for object-oriented databases and the semantic model using the SPARQL ontology-based search language. We compare the two query methods, discuss the results and explain the benefits of using semantics-based information retrieval techniques when dealing with business process information.

DESIDOC Journal of Library & Information Technology

Virtual Exhibitions are single- or multi-user realistic 3D representations of artifact collection... more Virtual Exhibitions are single- or multi-user realistic 3D representations of artifact collections, in which visitors navigate, observe the exhibits, learn related information about them presented in various media, and in some cases interact with them. Given that virtual exhibitions have no physical restrictions, they may host a limitless number of exhibits in a very large presentation space. On the other hand studies have shown that visitors have various goals concerning their experience within an exhibition space, they follow different navigation strategies in browsing the exhibits, and they may be interested only in parts of the collection. These differentiations among online users raise a need for adaptation and personalization of the 3D environment and its content. Researchers in Adaptive Hypermedia distinguish between adaptation of content, adaptation of presentation and modality, and adaptation of structure. In the case of Virtual Exhibitions the content can be adapted by dyn...

Lecture Notes in Computer Science, 2003

This paper discusses the use of intelligent planning as a control mechanism for agents situated i... more This paper discusses the use of intelligent planning as a control mechanism for agents situated in a virtual world. Virtual environments require a planning system that is flexible enough to handle situations impossible to predict before execution has started. In order to produce believable results, the planner should also be able to model and handle emotions. Working towards this direction, the authors propose a motivation-driven, continuous hierarchical planner as an appropriate paradigm.

Lecture Notes in Computer Science, 2005

IVAs and Education.- Training Agents: An Architecture for Reusability.- Ask&Answer: An Educat... more IVAs and Education.- Training Agents: An Architecture for Reusability.- Ask&Answer: An Educational Game Where It Pays to Endear Your Capricious Virtual Companion.- Conversational Agents/NLP.- Natural Behavior of a Listening Agent.- Providing Computer Game Characters with Conversational Abilities.- Fight, Flight, or Negotiate: Believable Strategies for Conversing Under Crisis.- Dialog Simulation for Background Characters.- IVA Architectures.- INTERFACE Toolkit: A New Tool for Building IVAs.- Autonomous Virtual Agents Learning a Cognitive Model and Evolving.- Using Real Objects to Communicate with Virtual Characters.- A Software Engineering Approach Combining Rational and Conversational Agents for the Design of Assistance Applications.- Marve: A Prototype Virtual Human Interface Framework for Studying Human-Virtual Human Interaction.- Cognition, Reasoning and Behaviour.- A Knowledge-Based Scenario Framework to Support Intelligent Planning Characters.- CAA: A Context-Sensitive Agent Architecture for Dynamic Virtual Environments.- When Emotion Does Not Mean Loss of Control.- Social Situated Agents in Virtual, Real and Mixed Reality Environments.- Do You See What Eyes See? Implementing Inattentional Blindness.- Social Causality and Responsibility: Modeling and Evaluation.- NonVerbal Communication.- Teaching Virtual Characters How to Use Body Language.- Direction of Attention Perception for Conversation Initiation in Virtual Environments.- A Model of Attention and Interest Using Gaze Behavior.- Where Do They Look? Gaze Behaviors of Multiple Users Interacting with an Embodied Conversational Agent.- Hierarchical Motion Controllers for Real-Time Autonomous Virtual Humans.- Modeling Dynamic Perceptual Attention in Complex Virtual Environments.- Storytelling/Interactive Narrative.- An Objective Character Believability Evaluation Procedure for Multi-agent Story Generation Systems.- Proactive Mediation in Plan-Based Narrative Environments.- FearNot! - An Experiment in Emergent Narrative.- Intelligent Virtual Agents in Collaborative Scenarios.- Social Intelligence.- A Conversational Agent as Museum Guide - Design and Evaluation of a Real-World Application.- Using Ontology to Establish Social Context and Support Social Reasoning.- Integrating Social Skills in Task-Oriented 3D IVA.- Emotions/Affect/Personality.- Emergent Affective and Personality Model.- Judging Laura: Perceived Qualities of a Mediated Human Versus an Embodied Agent.- The Significance of Textures for Affective Interfaces.- Levels of Representation in the Annotation of Emotion for the Specification of Expressivity in ECAs.- Extended Behavior Networks and Agent Personality: Investigating the Design of Character Stereotypes in the Game Unreal Tournament.- Evaluation and Methodology.- Direct Manipulation Like Tools for Designing Intelligent Virtual Agents.- Social Communicative Effects of a Virtual Program Guide.- Maintaining the Identity of Dynamically Embodied Agents.- The Behavior Oriented Design of an Unreal Tournament Character.- MyTutor: A Personal Tutoring Agent.- Poster Session.- Using Facial Expressions Depicting Emotions in a Human-Computer Interface Intended for People with Autism.- A Survey of Computational Emotion Research.- A Study on Generating and Matching Facial Control Point Using Radial Basis Function.- A Platform Independent Architecture for Virtual Characters and Avatars.- GAL: Towards Large Simulations with Tens of Agents.- Virtual Agents in a Simulation of an ISO-Company.- Appraisal for a Character-Based Story-World.- Evolving Emotional Behaviour for Expressive Performance of Music.- A Model of an Embodied Emotional Agent.- Agent Assistance for 3D World Navigation.- NeXuS: Delivering Perceptions to Situated Embodied Agents.- Emotion in Artificial Intelligence and Artificial Life Research: Facing Problems.- A Synthetic Agent for Mentoring Novice Programmers Within a Desktop Computer Environment.- vBroker: Agents Teaching Stock Market.- Emergence of Representational Structures in Virtual Agents.