Michail Vaitis | University of the Aegean (original) (raw)
Papers by Michail Vaitis
Journal of Network and Computer Applications, 2003
Driven by the philosophy of the 'primacy of structure over data', Component-Based Open Hypermedia... more Driven by the philosophy of the 'primacy of structure over data', Component-Based Open Hypermedia Systems (CB-OHS) present an open set of structure servers providing structural abstractions of different hypermedia domains. To address the emergent requirements and to facilitate the development of structure servers, structure should be handled as a first class entity. We propose patterns for structure, called templates, that define the structural model upon which structure servers operate. We present how structure servers are developed and operate in the Callimachus CB-OHS. Development of structure servers within Callimachus is based on the explicit specification of structure with the use of an atomic structural primitive called the structural element. Explicit structure specification eases the development of structure servers in CB-OHS, making such development less error prone and providing the basis for tailoring domain specific abstractions.
Springer eBooks, 1996
ABSTRACT This paper presents a methodology for constructing hypertext views over existing relatio... more ABSTRACT This paper presents a methodology for constructing hypertext views over existing relational databases. First, the database semantics are extracted in the form of an EER schema, using database reverse engineering techniques. Then, the EER schema is used for the definition of the node and link types of hypertext views. This two-stage approach has the benefit that the hypertext designer considers only a conceptual model of the database. Moreover, the instances of node and link types are dynamically computed; no data replication takes place. An experimental set of tools that support the methodology has been developed and used in a realistic case study.
Heritage, May 12, 2019
Dynamic processes in coastal zones and human activities in the coastal environment produce pressu... more Dynamic processes in coastal zones and human activities in the coastal environment produce pressure on cultural heritage, especially in touristic places. Unmanned aerial systems (UAS) are used as an additional tool for monitoring cultural heritage sites in sensitive coastal areas. UASs provide low-cost accurate spatial data and high-resolution imagery products in various spatial and temporal scales. The use of UAS for mapping cultural heritage sites in the coastal zone is of increasing interest among scientists and archaeologists in terms of monitoring, documentation, mapping, and restoration. This study outlines the integration of UAS data acquisition and structure from motion (SfM) pipeline for the visualization of selected cultural heritage areas (ancient harbors) in the coastal zone. The UAS-SfM methodology produces very detailed orthophoto maps for mapping and detecting cultural heritage sites. Additionally, a metadata cataloging system has been developed in order to facilitate online searching operations for all products of the data acquisition, SfM pipeline, and cartographic processes. For this reason, a specific metadata profile was implemented, based on the European INSPIRE framework. As a result, datasets reusability and catalogs interoperability are promoted.
EGU General Assembly Conference Abstracts, Apr 1, 2016
In the real estate business, it is a common understanding that the value and potential of a prope... more In the real estate business, it is a common understanding that the value and potential of a property are fundamentally determined by its location and surrounding environment, like the proximity to services and facilities. Depending on buyer/tenant preferences or on the stage of a person life cycle, surrounding preferences may vary, such as families with young children are interested in properties located near parks, playgrounds or schools, whereas young people and students want to be near entertainment venues. In this paper, we present "Rate your Place", a web-based GIS that allows buyers/tenants to define their preferences regarding the types of facilities that they want to have near or far from their ideal property and returns a ranked list of the most suitable properties. Ranking mechanism is based on a multi-criteria geospatial analysis methodology that employs: (a) routing methods, for calculating road network distances, (b) a Ratio Estimation Procedure, for assigning weights to types of facilities, (c) Score Range Procedure, for distance normalization and (d) a Simple Additive Weighting (SAW) index for calculating the final score of each property. The methodology is supported by an integrated web-based GIS developed exclusively with the use of open source software. As a case study, an application has been implemented for the city of Chios, Greece.
Springer eBooks, 2005
ABSTRACT Geoportals (geographic portals) are entry points on the Web, where various geographic in... more ABSTRACT Geoportals (geographic portals) are entry points on the Web, where various geographic information resources can be easily discovered. They organize geospatial data and services through catalogs containing metadata records, which can be queried in order to give access to related resources. However, the current organization of geographic information in metadata catalogs is unable to capture the semantics of the data being described; therefore users often miss geographical resources of interest when searching for geospatial data in the World Wide Web. In this paper, we present an innovative approach in the development of geoportals, based on the next generation of the Web, called the Semantic Web. This approach relies in the organization of the geo-data at the semantic level through appropriate geographic ontologies, and the exploitation of this organization through the user interface of the geoportal. To the best of our knowledge, this approach is the first that combines the expressiveness of geo-ontologies in the context of geographic portals.
Natural Hazards and Earth System Sciences, Dec 5, 2011
With the proliferation of the geospatial technologies on the Internet, the role of geo-portals (i... more With the proliferation of the geospatial technologies on the Internet, the role of geo-portals (i.e. gateways to Spatial Data Infrastructures) in the area of wildfires management emerges. However, keyword-based techniques often frustrate users when looking for data of interest in geo-portal environments, while little attention has been paid to shift from the conventional keyword-based to navigation-based mechanisms. The presented OntoFire system is an ontologybased geo-portal about wildfires. Through the proposed navigation mechanisms, the relationships between the data can be discovered, which would otherwise not be possible when using conventional querying techniques alone. End users can use the browsing interface to find resources of interest by using the navigation mechanisms provided. Data providers can use the publishing interface to submit new metadata, modify metadata or removing metadata in/from the catalogue. The proposed approach can improve the discovery of valuable information that is necessary to set priorities for disaster mitigation and prevention strategies. OntoFire aspires to be a focal point of integration and management of a very large amount of information, contributing in this way to the dissemination of knowledge and to the preparedness of the operational stakeholders.
Computers & Geosciences, Feb 1, 2009
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d m a n u s c r i p t Towards a semantics-based approach in the development of geographic portals
Journal on Data Semantics, Dec 1, 2020
The growth of Web of Data led to the development of dataset recommendation methodologies, which a... more The growth of Web of Data led to the development of dataset recommendation methodologies, which automate the discovery of datasets that may contain same or related instances (i.e., objects), in order to be used as input for several tasks including Link Discovery. The recommendation process takes as input one dataset (or any tripleset) and proposes other datasets which are the most likely to contain related instances. Existing recommenders determine the relevance between datasets by comparing their textual and structural similarity or by examining existing links among them. In this paper, we determine relevancy by comparing the geospatial relatedness of triplesets containing instances belonging to spatial classes (that is, classes containing instances whose locations are georeferenced by point geometries) based on the hypothesis that pairs of classes whose instances present similar spatial distribution are likely to contain semantically related instances. The proposed methodology builds summaries that capture the spatial distribution of classes. It utilizes the summaries, first, to rule out irrelevant (to an input class) classes by applying spatial filters and, then, to rank the remaining classes by applying a geospatial relatedness measure, so as the top ranked classes are more probable to contain related instances. The methodology's evaluation contains an exploration of Web of Data spatial classes characteristics and a discussion of the experiment results that validate our hypothesis. We show that the spatial filtering reduces effectively and efficiently up to 99% the search space for relevant classes in Web of Data and that the proposed geospatial relatedness measures generate ranked lists of recommended classes with 62% mean average precision, approximately 35% higher than simple baselines.
Lecture notes in geoinformation and cartography, 2006
ABSTRACT Despite the evolving technological developments that have influenced spatial information... more ABSTRACT Despite the evolving technological developments that have influenced spatial information management and communication, digital cartography has to overcome a number of issues concerning cognition and usability. Hypermaps, integrating concepts from geographical information systems and hypermedia systems, have been proposed by many researchers as a promising solution. However, these systems are isolated, without making an attempt for information and services exchange. In this chapter, inspired by previous work on Open Hypermedia Systems, we propose a conceptual reference model for cartographic hypermedia services. As a prerequisite, a number of hypermap systems have been studied, resulting in a set of indispensable requirements.
Lecture Notes in Computer Science, 2004
Earth Science Informatics, Jun 26, 2018
Climate information is important for scientific research and decision making. Nowadays web-based ... more Climate information is important for scientific research and decision making. Nowadays web-based cartography technologies provide the means for wide dissemination of such information. This paper describes the design and implementation of a spatial database and a web-GIS application that allow the management, visualization and analysis of data that are directly or indirectly related to climate and its future projections in Greece. Emphasis is given to the design decisions made in order to fulfill the requirements of flexible data querying and reporting, and of maintenance cost minimization. Cartographic layers for climatic and other parameters are dynamically produced through database views and geographic web services. The web-GIS provides userfriendly cartographic operations for visualizing and manipulating thematic maps, as well as reporting services for selecting, displaying and downloading climatic values for selected areas.
Lecture Notes in Computer Science, 2000
... Michalis Vaitis1,2, Athanasios Papadopoulos1,2, Manolis Tzagarakis1,2, and Dimitris Christodo... more ... Michalis Vaitis1,2, Athanasios Papadopoulos1,2, Manolis Tzagarakis1,2, and Dimitris Christodoulakis1,2 ... The well-known and very important hypermedia domains (navigational, taxonomic, spatial, etc.) are just instances of an un-restricted space of relationship types. ...
Review of International Geographical Education Online, 2017
Island studies journal, May 1, 2017
Information systems play a crucial role in supporting decision-making for managing and administra... more Information systems play a crucial role in supporting decision-making for managing and administrating territories at different levels of authority. Unfortunately, most such information systems are not dedicated to or customized for the special needs imposed by islands. In this work we describe the design, implementation, and operation of the 'Archipelago' digital repository, an integrated information system for supporting island research and development. The main objectives of the system are the storage, documentation, and dissemination of any kind of data regarding islands, as well as the provision of cartographic facilities for searching, visualization, and comparison. The basic principle of the system is the ability to geographically designate any stored material. The system is compatible with the standards for digital information documentation and interoperability, and it is based on free and open-source software tools.
Springer eBooks, Jun 1, 2012
Journal of Network and Computer Applications, 2003
Driven by the philosophy of the 'primacy of structure over data', Component-Based Open Hypermedia... more Driven by the philosophy of the 'primacy of structure over data', Component-Based Open Hypermedia Systems (CB-OHS) present an open set of structure servers providing structural abstractions of different hypermedia domains. To address the emergent requirements and to facilitate the development of structure servers, structure should be handled as a first class entity. We propose patterns for structure, called templates, that define the structural model upon which structure servers operate. We present how structure servers are developed and operate in the Callimachus CB-OHS. Development of structure servers within Callimachus is based on the explicit specification of structure with the use of an atomic structural primitive called the structural element. Explicit structure specification eases the development of structure servers in CB-OHS, making such development less error prone and providing the basis for tailoring domain specific abstractions.
Springer eBooks, 1996
ABSTRACT This paper presents a methodology for constructing hypertext views over existing relatio... more ABSTRACT This paper presents a methodology for constructing hypertext views over existing relational databases. First, the database semantics are extracted in the form of an EER schema, using database reverse engineering techniques. Then, the EER schema is used for the definition of the node and link types of hypertext views. This two-stage approach has the benefit that the hypertext designer considers only a conceptual model of the database. Moreover, the instances of node and link types are dynamically computed; no data replication takes place. An experimental set of tools that support the methodology has been developed and used in a realistic case study.
Heritage, May 12, 2019
Dynamic processes in coastal zones and human activities in the coastal environment produce pressu... more Dynamic processes in coastal zones and human activities in the coastal environment produce pressure on cultural heritage, especially in touristic places. Unmanned aerial systems (UAS) are used as an additional tool for monitoring cultural heritage sites in sensitive coastal areas. UASs provide low-cost accurate spatial data and high-resolution imagery products in various spatial and temporal scales. The use of UAS for mapping cultural heritage sites in the coastal zone is of increasing interest among scientists and archaeologists in terms of monitoring, documentation, mapping, and restoration. This study outlines the integration of UAS data acquisition and structure from motion (SfM) pipeline for the visualization of selected cultural heritage areas (ancient harbors) in the coastal zone. The UAS-SfM methodology produces very detailed orthophoto maps for mapping and detecting cultural heritage sites. Additionally, a metadata cataloging system has been developed in order to facilitate online searching operations for all products of the data acquisition, SfM pipeline, and cartographic processes. For this reason, a specific metadata profile was implemented, based on the European INSPIRE framework. As a result, datasets reusability and catalogs interoperability are promoted.
EGU General Assembly Conference Abstracts, Apr 1, 2016
In the real estate business, it is a common understanding that the value and potential of a prope... more In the real estate business, it is a common understanding that the value and potential of a property are fundamentally determined by its location and surrounding environment, like the proximity to services and facilities. Depending on buyer/tenant preferences or on the stage of a person life cycle, surrounding preferences may vary, such as families with young children are interested in properties located near parks, playgrounds or schools, whereas young people and students want to be near entertainment venues. In this paper, we present "Rate your Place", a web-based GIS that allows buyers/tenants to define their preferences regarding the types of facilities that they want to have near or far from their ideal property and returns a ranked list of the most suitable properties. Ranking mechanism is based on a multi-criteria geospatial analysis methodology that employs: (a) routing methods, for calculating road network distances, (b) a Ratio Estimation Procedure, for assigning weights to types of facilities, (c) Score Range Procedure, for distance normalization and (d) a Simple Additive Weighting (SAW) index for calculating the final score of each property. The methodology is supported by an integrated web-based GIS developed exclusively with the use of open source software. As a case study, an application has been implemented for the city of Chios, Greece.
Springer eBooks, 2005
ABSTRACT Geoportals (geographic portals) are entry points on the Web, where various geographic in... more ABSTRACT Geoportals (geographic portals) are entry points on the Web, where various geographic information resources can be easily discovered. They organize geospatial data and services through catalogs containing metadata records, which can be queried in order to give access to related resources. However, the current organization of geographic information in metadata catalogs is unable to capture the semantics of the data being described; therefore users often miss geographical resources of interest when searching for geospatial data in the World Wide Web. In this paper, we present an innovative approach in the development of geoportals, based on the next generation of the Web, called the Semantic Web. This approach relies in the organization of the geo-data at the semantic level through appropriate geographic ontologies, and the exploitation of this organization through the user interface of the geoportal. To the best of our knowledge, this approach is the first that combines the expressiveness of geo-ontologies in the context of geographic portals.
Natural Hazards and Earth System Sciences, Dec 5, 2011
With the proliferation of the geospatial technologies on the Internet, the role of geo-portals (i... more With the proliferation of the geospatial technologies on the Internet, the role of geo-portals (i.e. gateways to Spatial Data Infrastructures) in the area of wildfires management emerges. However, keyword-based techniques often frustrate users when looking for data of interest in geo-portal environments, while little attention has been paid to shift from the conventional keyword-based to navigation-based mechanisms. The presented OntoFire system is an ontologybased geo-portal about wildfires. Through the proposed navigation mechanisms, the relationships between the data can be discovered, which would otherwise not be possible when using conventional querying techniques alone. End users can use the browsing interface to find resources of interest by using the navigation mechanisms provided. Data providers can use the publishing interface to submit new metadata, modify metadata or removing metadata in/from the catalogue. The proposed approach can improve the discovery of valuable information that is necessary to set priorities for disaster mitigation and prevention strategies. OntoFire aspires to be a focal point of integration and management of a very large amount of information, contributing in this way to the dissemination of knowledge and to the preparedness of the operational stakeholders.
Computers & Geosciences, Feb 1, 2009
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d m a n u s c r i p t Towards a semantics-based approach in the development of geographic portals
Journal on Data Semantics, Dec 1, 2020
The growth of Web of Data led to the development of dataset recommendation methodologies, which a... more The growth of Web of Data led to the development of dataset recommendation methodologies, which automate the discovery of datasets that may contain same or related instances (i.e., objects), in order to be used as input for several tasks including Link Discovery. The recommendation process takes as input one dataset (or any tripleset) and proposes other datasets which are the most likely to contain related instances. Existing recommenders determine the relevance between datasets by comparing their textual and structural similarity or by examining existing links among them. In this paper, we determine relevancy by comparing the geospatial relatedness of triplesets containing instances belonging to spatial classes (that is, classes containing instances whose locations are georeferenced by point geometries) based on the hypothesis that pairs of classes whose instances present similar spatial distribution are likely to contain semantically related instances. The proposed methodology builds summaries that capture the spatial distribution of classes. It utilizes the summaries, first, to rule out irrelevant (to an input class) classes by applying spatial filters and, then, to rank the remaining classes by applying a geospatial relatedness measure, so as the top ranked classes are more probable to contain related instances. The methodology's evaluation contains an exploration of Web of Data spatial classes characteristics and a discussion of the experiment results that validate our hypothesis. We show that the spatial filtering reduces effectively and efficiently up to 99% the search space for relevant classes in Web of Data and that the proposed geospatial relatedness measures generate ranked lists of recommended classes with 62% mean average precision, approximately 35% higher than simple baselines.
Lecture notes in geoinformation and cartography, 2006
ABSTRACT Despite the evolving technological developments that have influenced spatial information... more ABSTRACT Despite the evolving technological developments that have influenced spatial information management and communication, digital cartography has to overcome a number of issues concerning cognition and usability. Hypermaps, integrating concepts from geographical information systems and hypermedia systems, have been proposed by many researchers as a promising solution. However, these systems are isolated, without making an attempt for information and services exchange. In this chapter, inspired by previous work on Open Hypermedia Systems, we propose a conceptual reference model for cartographic hypermedia services. As a prerequisite, a number of hypermap systems have been studied, resulting in a set of indispensable requirements.
Lecture Notes in Computer Science, 2004
Earth Science Informatics, Jun 26, 2018
Climate information is important for scientific research and decision making. Nowadays web-based ... more Climate information is important for scientific research and decision making. Nowadays web-based cartography technologies provide the means for wide dissemination of such information. This paper describes the design and implementation of a spatial database and a web-GIS application that allow the management, visualization and analysis of data that are directly or indirectly related to climate and its future projections in Greece. Emphasis is given to the design decisions made in order to fulfill the requirements of flexible data querying and reporting, and of maintenance cost minimization. Cartographic layers for climatic and other parameters are dynamically produced through database views and geographic web services. The web-GIS provides userfriendly cartographic operations for visualizing and manipulating thematic maps, as well as reporting services for selecting, displaying and downloading climatic values for selected areas.
Lecture Notes in Computer Science, 2000
... Michalis Vaitis1,2, Athanasios Papadopoulos1,2, Manolis Tzagarakis1,2, and Dimitris Christodo... more ... Michalis Vaitis1,2, Athanasios Papadopoulos1,2, Manolis Tzagarakis1,2, and Dimitris Christodoulakis1,2 ... The well-known and very important hypermedia domains (navigational, taxonomic, spatial, etc.) are just instances of an un-restricted space of relationship types. ...
Review of International Geographical Education Online, 2017
Island studies journal, May 1, 2017
Information systems play a crucial role in supporting decision-making for managing and administra... more Information systems play a crucial role in supporting decision-making for managing and administrating territories at different levels of authority. Unfortunately, most such information systems are not dedicated to or customized for the special needs imposed by islands. In this work we describe the design, implementation, and operation of the 'Archipelago' digital repository, an integrated information system for supporting island research and development. The main objectives of the system are the storage, documentation, and dissemination of any kind of data regarding islands, as well as the provision of cartographic facilities for searching, visualization, and comparison. The basic principle of the system is the ability to geographically designate any stored material. The system is compatible with the standards for digital information documentation and interoperability, and it is based on free and open-source software tools.
Springer eBooks, Jun 1, 2012
Η δημιουργία του Άτλαντα των Ελλη- νικών νησιών αποτελεί έναν στόχο που τέθη- κε από την εποχή τη... more Η δημιουργία του Άτλαντα των Ελλη-
νικών νησιών αποτελεί έναν στόχο που τέθη-
κε από την εποχή της δημιουργίας του Εργα-
στηρίου Τοπικής και Νησιωτικής Ανάπτυ-
ξης to 1992 αφού θεωρήθηκε ότι η σοβαρή
ενασχόληση με τα νησιά απαιτεί από τη μία
πλευρά τη θεωρητική τεκμηρίωση των ιδι-
αιτεροτήτων του νησιωτικού χώρου και των
πολιτικών εκείνων που μπορούν να αντιμε-
τωπίσουν τα προβλήματα που πηγάζουν από
τα χαρακτηριστικά αυτά αξιοποιώντας τις
σύγχρονες ευκαιρίες και προκλήσεις και από
την άλλη πλευρά τη συστηματική τεκμηρίω-
ση με δεδομένα σε ότι αφορά τα φυσικά χα-
ρακτηριστικά των νησιών, τις κοινωνικοοι-
κονομικές εξελίξεις αλλά και τη κατάσταση
του περιβάλλοντος. Έγιναν πολλές προσπά-
θειες στο παρελθόν μέσα από τη συμμετοχή
σε διάφορα δίκτυα και προγράμματα όπως
το EURISLES τη δεκαετία του ’90 και το EUROISLANDS
πριν μερικά χρόνια.
Το πρόγραμμα «Το Πανεπιστήμιο Αι-
γαίου, ως βασικός παράγοντας για την οικο-
νομική και κοινωνική ανάπτυξη του Αιγαιο-
πελαγίτικου χώρου» του Υπουργείου Εθνικής
Παιδείας και Θρησκευμάτων με τη χρημα-
τοδότηση της προσπάθειας να καταστεί το
Πανεπιστήμιο Αιγαίου διεθνές κέντρο αρι-
στείας στα θέματα νησιωτικότητας μέσα από
τη σύνδεση της έρευνας με την εκπαίδευση
και τη διεθνή κοινότητα, έδωσε έμφαση σε
δύο ενέργειες:
1. Τη συγκέντρωση και ανάλυση της βι-
βλιογραφίας στα βασικά θέματα που
απασχολούν τα νησιά με τη δημιουρ-
γία ενός ηλεκτρονικού αποθετηρίου
(www.archipelago.aegean.gr)
2. Τη δημιουργία του Άτλαντα των Ελληνι-
κών Νησιών
Το έντυπο που έχετε σήμερα στα χέρια
σας αποτελεί μια προσπάθεια για μια πρώτη
έντυπη συστηματική αποτύπωση των βασι-
κών θεμάτων που απασχολούν τα νησιά με
δεδομένα, πίνακες, χάρτες και αναλύσεις.
Όμως ο Άτλαντας δεν σταματά εδώ, εδώ αρ-
χίζει. Η δημιουργία του Άτλαντα βασίζεται σε
μια βάση δεδομένων που για να παραμείνει
χρήσιμη πρέπει να ενημερώνεται διαρκώς
και να προχωρά σε επικαιροποίηση των ανα-
λύσεων. Ο Άτλαντας δεν φιλοδοξεί να υπο-
καταστήσει την Ελληνική Στατιστική Αρχή.
Βασίζεται στα στοιχεία που αυτή παράγει
κάτω από μία κλαδική λογική για να παράξει
χωρική πληροφορία για μια ιδιόμορφη και
πολλές δυσκολίες περιοχή όπως είναι τα νη-
σιά.
Γ.Σπιλάνης
Θ.Κίζος
This article presents a geocaching educational system called RouteQuizer that consists of an Andr... more This article presents a geocaching educational system called RouteQuizer that consists of an Android application, a web application and an online database. It motivates students to visit various geographic points of interest and answer site-related questions of multiple choice type. The android application used by the students, takes advantage of the navigation (GPS) and internet connectivity features of their smartphones. The web application is used by tutors, to create dynamic location-based educational games for their students. The database stores data such as site information and coordinates, questions and answers regarding the area of interest, as well as students' performance results. There are no geographical restrictions and no limits regarding the number of destinations, thus making the application usable from everyone everywhere.