This paper describes research work carried out with the aim to investigate dynamically evolving d... more This paper describes research work carried out with the aim to investigate dynamically evolving database environments and corresponding schemata, allowing storage and manipulation of variable length data, a variable number of fields per record, variable length records, manipulation of authority records and links between records and fields, and dynamically defined objects (relations in the traditional sense). The paper proposes a new framework for the definition of a unified schema that eliminates completely the need for reorganisation at both logical and internal levels. Retrieval of data is optimised through self‐contained storage chunks that also vary dynamically.
-In this paper we present a system for writer identification from historical lines of text, where... more -In this paper we present a system for writer identification from historical lines of text, where features are extracted and used to recognize individuals. The main goal is to analyze documents of different writing styles in order to identify the writers. We consider a complete 2D probability distribution that takes into account all possible combinations of angle pairs, outperforming original code. The images included are taken from the Greek digital library Hellinomnimon available at http://www.lib.uoa.gr/hellinomnimon/. The experiments are based on 7 pages of text written by 43 different writers. Keywords-Writer identification, Handwriting analysis, Feature extraction, Edge-hinge distribution, Historical documents.
2016 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining (ASONAM), 2016
The study of a large real world network in terms of graph sample representation constitutes a ver... more The study of a large real world network in terms of graph sample representation constitutes a very powerful and useful tool in several domains of network analysis. This is the motivation that has led the work of this paper towards the development of a new graph sampling algorithm. Previous research in this area proposed simple processes such as the classic Random Walk algorithm, Random node and Random edge sampling and has evolved during the last decade to more advanced graph exploration approaches such as Forest Fire and Frontier sampling. In this paper, we propose a new graph sampling method based on edge selection. In addition, we crawled Facebook collecting a large dataset consisting of 10 million users and 80 million users' relations, which we have also used to evaluate our sampling algorithm. The experimental evaluation on several datasets proves that our approach preserves several properties of the initial graphs, leading to representative samples and outperforms all the other approaches.
The Tarski model allows for the simulation of various database models, using an algebraic formula... more The Tarski model allows for the simulation of various database models, using an algebraic formulation, persistent. We shall show how the Frame DataBase (FDB) model together with its language Conceptual Universal Database Language (CUDL) can be expressed in the Tarski model. We model ,an FDB database by a ,set of mathematical ,relations and manipulate ,the database by performing,Tarski algebraic
The complex nature of real world networks is a central subject in several disciplines, from Physi... more The complex nature of real world networks is a central subject in several disciplines, from Physics to computer science. The complex network dynamics of peers communication and information exchange are specified to a large degree by the most efficient spreaders - the entities that play a central role in various ways such as the viruses propagation, the diffusion of information, the viral marketing and net- work vulnerability to external attacks. In this paper, we deal with the problem of identifying the influential spreaders of a complex network when either the network is very large or else we have limited computational capabilities to compute global centrality measures. Our approach is based on graph sampling and specifically on Rank Degree, a newly published graph exploration sampling method. We conduct extensive experiments in five real world networks using four centrality metrics for the nodes spreading efficiency. We present strong evidence that our method is highly effective. By sampling 30% of the network and using at least two out of four centrality measures, we can identify more than 80% of the influential spreaders, while at the same time, preserving the original ranking to a large extent.
The study of a large real world network in terms of graph sample representation constitutes a ver... more The study of a large real world network in terms of graph sample representation constitutes a very powerful and useful tool in several domains of network analysis. This is the motivation that has led the work of this paper towards the development of a new graph sampling algorithm. Previous research in this area proposed simple processes such as the classic Random Walk algorithm, Random node and Random edge sampling and has evolved during the last decade to more advanced graph exploration approaches such as Forest Fire and Frontier sampling. In this paper, we propose a new graph sampling method based on edge selection. In addition, we crawled Facebook collecting a large dataset consisting of 10 million users and 80 million users’ relations, which we have also used to evaluate our sampling algorithm. The experimental evaluation on several datasets proves that our approach preserves several properties of the initial graphs, leading to representative samples and outperforms all the othe...
2015 International Conference on Industrial Engineering and Operations Management, Mar 1, 2015
ABSTRACT This paper outlines the architecture of the ARISTON expert system shell for vocational c... more ABSTRACT This paper outlines the architecture of the ARISTON expert system shell for vocational counselling. The information system prompts the user to answer a series of psychometric questions, for a period of approximately 40 minutes. The system then analyses the answers and creates a report automatically and sends this to the e-mail address of the user, with no human intervention. The report contains analytical conclusions regarding the personality of the individual, the motives behind choosing a career, aptitudes– abilities, and a list of approximately 30 professions / specialisations that match with the personality traits of the user. Herein, we show that expert human knowledge can be codified to support advanced vocational counselling tasks in an integrated manner, quantifying precisely personality traits, aptitudes, abilities, motivation, and preferences.
Η εργασία αυτή παρουσιάζει ένα έμπειρο σύστημα αξιολόγησης των μαθησιακών ικανοτήτων του ατόμου μ... more Η εργασία αυτή παρουσιάζει ένα έμπειρο σύστημα αξιολόγησης των μαθησιακών ικανοτήτων του ατόμου μέσω ενός ειδικά σχεδιασμένου ψυχομετρικού ερωτηματολογίου που στηρίζεται στη θεωρία του χωροχρονικού και του διαγραμματικού συλλογισμού. Όταν κάνουμε λόγο για «έμπειρο σύστημα», εννοούμε λογισμικό που έχει κωδικοποιημένη την ανθρώπινη εμπειρία και που έχει δομηθεί με βάση επαρκή και τεκμηριωμένη γνώση συγκεκριμένων μαθησιακών παραγόντων, που είναι: α) Συνταίριασμα εννοιών, β) Σύνθεση εννοιών, γ) Ανακατασκευή εννοιών, δ) Αναγνώριση αναλογιών, ε) Κατανόηση κανόνων, στ) Κατανόηση υποσυνόλων, και ζ) Κατανόηση τομών. Το ψυχομετρικό ερωτηματολόγιο είναι πλήρως αυτοματοποιημένο και η αναφορά με τα συμπεράσματα, παράγεται αυτόματα. Το έμπειρο σύστημα αξιοποιεί προχωρημένα μαθηματικά μοντέλα, χωρίς την παραμικρή επέμβαση συμβούλου, και, επομένως, είναι απαλλαγμένη από οποιοδήποτε υποκειμενικό στοιχείο. Όλη η γνώση που εμπεριέχει η συστοιχία ερωτήσεων που υιοθετούμε στηρίζεται σε στάθμιση που αφορ...
This paper describes research work carried out with the aim to investigate dynamically evolving d... more This paper describes research work carried out with the aim to investigate dynamically evolving database environments and corresponding schemata, allowing storage and manipulation of variable length data, a variable number of fields per record, variable length records, manipulation of authority records and links between records and fields, and dynamically defined objects (relations in the traditional sense). The paper proposes a new framework for the definition of a unified schema that eliminates completely the need for reorganisation at both logical and internal levels. Retrieval of data is optimised through self‐contained storage chunks that also vary dynamically.
-In this paper we present a system for writer identification from historical lines of text, where... more -In this paper we present a system for writer identification from historical lines of text, where features are extracted and used to recognize individuals. The main goal is to analyze documents of different writing styles in order to identify the writers. We consider a complete 2D probability distribution that takes into account all possible combinations of angle pairs, outperforming original code. The images included are taken from the Greek digital library Hellinomnimon available at http://www.lib.uoa.gr/hellinomnimon/. The experiments are based on 7 pages of text written by 43 different writers. Keywords-Writer identification, Handwriting analysis, Feature extraction, Edge-hinge distribution, Historical documents.
2016 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining (ASONAM), 2016
The study of a large real world network in terms of graph sample representation constitutes a ver... more The study of a large real world network in terms of graph sample representation constitutes a very powerful and useful tool in several domains of network analysis. This is the motivation that has led the work of this paper towards the development of a new graph sampling algorithm. Previous research in this area proposed simple processes such as the classic Random Walk algorithm, Random node and Random edge sampling and has evolved during the last decade to more advanced graph exploration approaches such as Forest Fire and Frontier sampling. In this paper, we propose a new graph sampling method based on edge selection. In addition, we crawled Facebook collecting a large dataset consisting of 10 million users and 80 million users' relations, which we have also used to evaluate our sampling algorithm. The experimental evaluation on several datasets proves that our approach preserves several properties of the initial graphs, leading to representative samples and outperforms all the other approaches.
The Tarski model allows for the simulation of various database models, using an algebraic formula... more The Tarski model allows for the simulation of various database models, using an algebraic formulation, persistent. We shall show how the Frame DataBase (FDB) model together with its language Conceptual Universal Database Language (CUDL) can be expressed in the Tarski model. We model ,an FDB database by a ,set of mathematical ,relations and manipulate ,the database by performing,Tarski algebraic
The complex nature of real world networks is a central subject in several disciplines, from Physi... more The complex nature of real world networks is a central subject in several disciplines, from Physics to computer science. The complex network dynamics of peers communication and information exchange are specified to a large degree by the most efficient spreaders - the entities that play a central role in various ways such as the viruses propagation, the diffusion of information, the viral marketing and net- work vulnerability to external attacks. In this paper, we deal with the problem of identifying the influential spreaders of a complex network when either the network is very large or else we have limited computational capabilities to compute global centrality measures. Our approach is based on graph sampling and specifically on Rank Degree, a newly published graph exploration sampling method. We conduct extensive experiments in five real world networks using four centrality metrics for the nodes spreading efficiency. We present strong evidence that our method is highly effective. By sampling 30% of the network and using at least two out of four centrality measures, we can identify more than 80% of the influential spreaders, while at the same time, preserving the original ranking to a large extent.
The study of a large real world network in terms of graph sample representation constitutes a ver... more The study of a large real world network in terms of graph sample representation constitutes a very powerful and useful tool in several domains of network analysis. This is the motivation that has led the work of this paper towards the development of a new graph sampling algorithm. Previous research in this area proposed simple processes such as the classic Random Walk algorithm, Random node and Random edge sampling and has evolved during the last decade to more advanced graph exploration approaches such as Forest Fire and Frontier sampling. In this paper, we propose a new graph sampling method based on edge selection. In addition, we crawled Facebook collecting a large dataset consisting of 10 million users and 80 million users’ relations, which we have also used to evaluate our sampling algorithm. The experimental evaluation on several datasets proves that our approach preserves several properties of the initial graphs, leading to representative samples and outperforms all the othe...
2015 International Conference on Industrial Engineering and Operations Management, Mar 1, 2015
ABSTRACT This paper outlines the architecture of the ARISTON expert system shell for vocational c... more ABSTRACT This paper outlines the architecture of the ARISTON expert system shell for vocational counselling. The information system prompts the user to answer a series of psychometric questions, for a period of approximately 40 minutes. The system then analyses the answers and creates a report automatically and sends this to the e-mail address of the user, with no human intervention. The report contains analytical conclusions regarding the personality of the individual, the motives behind choosing a career, aptitudes– abilities, and a list of approximately 30 professions / specialisations that match with the personality traits of the user. Herein, we show that expert human knowledge can be codified to support advanced vocational counselling tasks in an integrated manner, quantifying precisely personality traits, aptitudes, abilities, motivation, and preferences.
Η εργασία αυτή παρουσιάζει ένα έμπειρο σύστημα αξιολόγησης των μαθησιακών ικανοτήτων του ατόμου μ... more Η εργασία αυτή παρουσιάζει ένα έμπειρο σύστημα αξιολόγησης των μαθησιακών ικανοτήτων του ατόμου μέσω ενός ειδικά σχεδιασμένου ψυχομετρικού ερωτηματολογίου που στηρίζεται στη θεωρία του χωροχρονικού και του διαγραμματικού συλλογισμού. Όταν κάνουμε λόγο για «έμπειρο σύστημα», εννοούμε λογισμικό που έχει κωδικοποιημένη την ανθρώπινη εμπειρία και που έχει δομηθεί με βάση επαρκή και τεκμηριωμένη γνώση συγκεκριμένων μαθησιακών παραγόντων, που είναι: α) Συνταίριασμα εννοιών, β) Σύνθεση εννοιών, γ) Ανακατασκευή εννοιών, δ) Αναγνώριση αναλογιών, ε) Κατανόηση κανόνων, στ) Κατανόηση υποσυνόλων, και ζ) Κατανόηση τομών. Το ψυχομετρικό ερωτηματολόγιο είναι πλήρως αυτοματοποιημένο και η αναφορά με τα συμπεράσματα, παράγεται αυτόματα. Το έμπειρο σύστημα αξιοποιεί προχωρημένα μαθηματικά μοντέλα, χωρίς την παραμικρή επέμβαση συμβούλου, και, επομένως, είναι απαλλαγμένη από οποιοδήποτε υποκειμενικό στοιχείο. Όλη η γνώση που εμπεριέχει η συστοιχία ερωτήσεων που υιοθετούμε στηρίζεται σε στάθμιση που αφορ...
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