Tutorials

Strabon, stSPARQL and GeoSPARQL have been presented in the following tutorials of our group:

  • ISWC 2017 tutorial: ReQuLGD: Representation and Querying for Linked Geospatial Data.
  • Tutorial at the 16th International Semantic Web Conference 2017

    The Web of data has recently been populated with linked geospatial data as various geospatial data sources have been transformed into RDF and added to the linked data cloud (e.g., Geonames, Open Street Map, CORINE land cover etc.). Therefore, it is important to study how to represent geospatial data in RDF and how to query it using SPARQL. Researchers from the areas of Semantic Web and Linked Data have studied theses problems recently. The results of this research has been the development of geospatial extensions of RDF and SPARQL, and the implementation of geospatial RDF stores. In this tutorial, we present a comparative survey of current research in this area and point to directions for future work.

    Tutorial Overview

    This is a half-day tutorial and will be held on Saturday, October 21st, in the afternoon. A brief overview is provided below:

    Part 1: Introduction

    Part 2: Data models and query languages for linked geospatial data. We survey the recent geospatial extensions of RDF and SPARQL concentrating on the OGC standard GeoSPARQL and our own language stSPARQL. We also discuss proposals for geospatial Ontology Based Data Access (OBDA) with more emphasis on the OBDA framework of our system Ontop-spatial. Finally, we discuss the problem of querying incomplete geospatial information expressed using Semantic Web standards.

    Part 3: Implemented Systems. In this part of the tutorial, we present systems for storing and querying linked geospatial data. We distinguish these implementations into two categories: geospatial RDF stores and geospatially-enabled OBDA systems. We will describe the architectures of the surveyed systems and we will compare them in terms of functionality and performance. Demos of Strabon and Ontop-spatial will also be given by the presenters.

    Part 4: Open issues. This last part of this tutorial will be dedicated to the discussion of open issues. We will point out open problems in the area of data models and query languages, and we will discuss how we can improve the performance of GeoSPARQL query engines, both native and OBDA. For the latter problem, we will discuss how state-of-the-art approaches in the area of big geospatial data, and big RDF data query processing can be used to improve the performance of existing GeoSPARQL query engines.

    Tutorial material

    1. Github repository with examples (software, datasets, etc.) that will be used in the tutorial.

    2. Strabon website

    3. Geographica

    The slides for each part of the tutorial will be availalble soon in this section.

    References

    • Open Geospatial Consortium. GeoSPARQL - A geographic query language for RDF data. OGC Candidate Implementation Standard, 2012.
    • M. Koubarakis and K. Kyzirakos. Modeling and Querying Metadata in the Semantic Sensor Web: The Model stRDF and the Query Language stSPARQL. In Proceedings of the 7th Extended Semantic Web Conference, volume 6088 of LNCS, pages 425–439. Springer, 2010.
    • K. Kyzirakos, M. Karpathiotakis, and M. Koubarakis. Strabon: A Semantic Geospatial DBMS. In Proceedings of the 11th International Semantic Web Conference, volume 7649 of LNCS, pages 295–311. Springer, 2012.
    • C. Nikolaou and M. Koubarakis. Querying incomplete information in RDF with SPARQL. Artificial Intelligence, 237:138 – 171, 2016.
    • K. Bereta and M. Koubarakis. Ontop of Geospatial databases. In Proceedings of the 15th International Semantic Web Conference, Kobe, Japan, October 17–21, pages 37–52. Springer International Publishing, 2016.
    • S. Brüggemann, K. Bereta, G. Xiao, and M. Koubarakis. Ontology-Based Data Access for Maritime Security. In Proceedings of the 13th Extended Semantic Web Conference, Heraklion, Crete, Greece, May 29 - June 2, 2016, pages 741–757, 2016
    • D. Calvanese, G. De Giacomo, D. Lembo, M. Lenzerini, A. Poggi, and R. Rosati. Ontology-based Database Access. In Proceedings of the Fifteenth Italian Symposium on Advanced Database Systems, SEBD 2007, 17-20 June 2007, Torre Canne, Fasano, BR, Italy, pages 324–331, 2007.
    • G. Garbis, K. Kyzirakos, and M. Koubarakis. Geographica: A Benchmark for Geospatial RDF stores (long version). In Proceedings of the 12th International Semantic Web Conference, volume 8219 of Lecture Notes in Computer Science, pages 343–359. Springer, 2013.

    Presenters

    Manolis Koubarakis is a Professor in the Dept. of Informatics and Telecommunications, National and Kapodistrian University of Athens. He is a EurAI fellow. He previously held positions at the Dept. of Electronic and Computer Engineering , Technical University of Crete (Assistant and Associate Professor), the Dept. of Informatics, University of Athens (Visiting Researcher), the Dept. of Computation, UMIST(now University of Manchester) (Lecturer) and the Dept. of Computing, Imperial College, London (Research Associate). He has published more than 170 papers that have been widely cited in the areas of Artificial Intelligence (especially Knowledge Representation), Databases, Semantic Web and Linked Data. He previously held positions at the Dept. of Electronic and Computer Engineering , Technical University of Crete (Assistant and Associate Professor), the Dept. of Informatics, University of Athens (Visiting Researcher), the Dept. of Computation, UMIST(now University of Manchester) (Lecturer) and the Dept. of Computing, Imperial College, London (Research Associate). He currently teaches the following university courses: Artificial Intelligence, Knowledge Technologies and Data Structures and Programming Techniques. His research has been funded by the European Commission, the Greek General Secretariat for Research and Technology and industry sources.

    Konstantina Bereta is a research associate at the Management of Data, Information and Knowledge group, in the Dept. of Informatics and Telecommunications, National and Kapodistrian University of Athens. She is also a PhD candidate under the supervision of prof. Manolis Koubarakis and holds a BSc. and MSc. from the same department. She has worked as a scientific programmer and research associate in several EU FP7 projects. Her research interests focus in the areas of spatiotemporal databases, Semantic Web and Cloud Computing. She is the developer of Ontop-spatial, a geospatial extension of the system Ontop, which is currently the most efficient OBDA solution for geospatial information.

  • ESWC 2015 tutorial: Publishing and Interlinking Linked Geospatial Data.
  • RW 2012 tutorial: Data Models and Query Languages for Linked Geospatial Data.
  • Data Models and Query Languages for Linked Geospatial Data

    On September 6, 2012 Manolis Koubarakis, Kostis Kyzirakos and Charalampos Nikolaou presented an invited tutorial on data modeling, querying and reasoning for linked geospatial data in the Reasoning Web Summer School which took place in Vienna.

    The topics covered in the tutorial together with the relevant slides are given below:

    1. Introduction [pdf]

    2. Background in geospatial data modeling [pdf]

    3. Geospatial data in RDF - stSPARQL [pdf]

    4. Geospatial data in RDF - GeoSPARQL [pdf]

    5. Implemented RDF Stores with geospatial support [pdf]

    6. Geospatial information with description logics, OWL and rules [pdf]

    7. Conclusions, questions, discussion [pdf]

    There is also an accompanying tutorial paper:

    • M. Koubarakis, M. Karpathiotakis, K. Kyzirakos, C. Nikolaou, and M. Sioutis. Data Models and Query Languages for Linked Geospatial Data. Invited tutorial at the 8th Reasoning Web Summer School 2012 (RW 2012), Austria, Vienna, 03-08 September, 2012. [pdf]

    For some more interesting tutorials given at the Reasoning Web Summer School see http://www.kr.tuwien.ac.at/events/rw2012.

  • ESWC 2012 tutorial: Data models, Query Languages, Implemented Systems and Applications of Linked Geospatial Data.
  • Data models, Query Languages, Implemented Systems and Applications of Linked Geospatial Data

    In this tutorial we survey the state of the art in data models, query languages, implemented systems and applications of linked geospatial data. Many kinds of geospatial data are becoming available as linked datasets given the proliferation of geospatial information on the Web (e.g., Google and Bing maps, user-generated geospatial content etc.). The topic of the tutorial is related to all core research areas of the Semantic Web (e.g., semantic information extraction, data modeling and ontologies, querying, reasoning, implemented systems etc.) since there is often a need to re-consider existing core techniques when we deal with geospatial information. Thus, it is timely to train Semantic Web researchers, especially the ones that are in the early stages of their careers, on the state of the art of this area and invite them to contribute to it.

    Tutorial description

    We have recently witnessed a proliferation of geospatial data on the Web. In addition to professionally-produced material being offered for free (e.g., Google or Bing maps), the public has also been encouraged to make geospatial content, including their geographical location, available online. The volume of such geospatial Web content is already big and constantly growing.

    Semantic Web researchers and practitioners have also started to make geospatial data available as linked data (e.g., Ordnance Survey, Great Britain's national mapping agency, makes available some of its geospatial data as linked data (http://data.ordnancesurvey.co.uk/.html), the portal LinkedGeoData makes OpenStreetMap data are made available as RDF (http://linkedgeodata.org/ etc.). Since a lot of data useful to the wider public is geospatial (e.g., open government data), we expect this trend to continue in the near future.

    In this tutorial we will present the state of the art in data models, query languages and implemented systems for linked geospatial data i.e., geospatial data expressed in RDF.

    Intended audience - Prerequisite knowledge

    The tutorial is targeted towards Semantic Web researchers in the early stages of their career. The prerequisite is good knowledge of RDF and SPARQL and some knowledge of other Semantic Web technologies (OWL, RDF stores, linked data). Knowledge of geospatial technologies is not a prerequisite and will be covered in some depth.

    Detailed description

    14:00-14:15 Introduction [Presentation: ppt | pdf]

    14:15-15:00 Background in geospatial data modeling [Presentation: ppt | pdf]

    • GIS concepts and vocabulary
    • Geographic space modeling and representation (vector space representation, half-space representation)
    • Co-ordinate systems
    • Relevant OGC standards (Well Known Text, Geography Markup Language)

    15:00-15:30 Geospatial data in the Semantic Web - stSPARQL [Presentation: ppt | pdf]

    • Representing geospatial data in stRDF
    • Examples of publicly available linked geospatial data
    • Querying geospatial data using stSPARQL

    15:30-16:00 Coffee Break

    16:00-16:30 Geospatial data in the Semantic Web - GeoSPARQL [Presentation: ppt | pdf]

    • The query language GeoSPARQL.

    16:30-16:45 Implemented systems [Presentation: ppt | pdf]

    • Survey of implementations of stSPARQL, GeoSPARQL and other research prototypes
    • Survey of geospatial features in well-known RDF stores

    16:50-17:00 Applications [Presentation: ppt | pdf]

    • Survey of existing applications of linked geospatial data. Emphasis on an application the presenters have developed on Earth Observation data.

    17:00 - 17:15 Conclusions, questions, discussion [Presentation: ppt | pdf]

    17:15 - 17:30 Demo of Strabon

    Presenter CVs

    Manolis Koubarakis is a Professor in the Dept. of Informatics and Telecommunications, National and Kapodistrian University of Athens. He has a degree in Mathematics from the University of Crete, an M.Sc. in Computer Science from the University of Toronto, and a Ph.D. in Computer Science from the National Technical University of Athens. He joined his current department in September 2005 as an Associate Professor and was promoted to Professor in April 2011. Before coming to Athens, he has been an Assistant and Associate Professor in the Dept. of Electronic and Computer Engineering, Technical University of Crete, and a Lecturer in the Dept. of Computation, University of Manchester – Institute of Science and Technology (UMIST). Manolis has published more than 100 papers that have been widely cited in the areas of Artificial Intelligence (especially Knowledge Representation), Databases, Semantic Web and P2P Computing. His research has been financially supported by the European Commission (projects CHOROCHRONOS, DIET, BRIDGEMAP, Evergrow, OntoGrid, SemsorGrid4Env and TELEIOS), the Greek General Secretariat for Research and Technology and industry sources (Microsoft Research and British Telecommunications). He is currently co-ordinating project TELEIOS (http://www.earthobservatory.eu/) which is building an Earth Observatory using a combination of technologies based on semantics (geospatial extensions of RDF and SPARQL) and array extensions of SQL. Manolis has 16 years teaching experience in academic institutions in Greece and the United Kingdom, and has given many talks in international conferences and workshops (some of them invited). He has served as Tutorial chair for ESWC 2011.

    Kostis Kyzirakos is a researcher in the Department of Informatics and Telecommunications, University of Athens. He received his Diploma in Engineering from the School of Electrical and Computer Engineering, NTUA, Athens. He has participated in projects funded by the European Commision (Ontogrid, SemsorGrid4Env, TELEIOS) and the Greek General Secretariat for Research and Technology (P2P Techniques for Semantic Web Services). He is one of the main developers of the semantic geospatial DBMS Strabon that was developed in the context of the EU projects SemsorGrid4Env and TELEIOS. In the same context, he studied and proposed how to represent and query geospatial data in the Semantic Web, published various geospatial datasets as linked geospatial data and implemented applications combining these data with previously published linked geospatial data. His current research focuses on modeling and querying semantic spatio-temporal information on top of traditional DBMS. He has given a tutorial on building semantic sensor webs and applications at ESWC 2011.

    Manos Karpathiotakis is a researcher in the Department of Informatics and Telecommunications, University of Athens. He received his Bachelor degree and his Master of Science from the Department of Informatics and Telecommunications of the University of Athens. He has participated in projects funded by the European Commision (TELEIOS, SemsorGrid4Env) and he is one of the main developers of the semantic geospatial DBMS Strabon that was developed in the context of these projects. In the same context, he published various geospatial datasets as linked geospatial data and implemented applications combining these data with previously published linked geospatial data. His current research focuses on the overlapping areas of Geospatial Semantic Web, Semantic Sensor Web and Linked Data.



Demo

  1. Wildfire Monitoring: The demo builds on the work in project TELEIOS where satellite images from the MSG/SEVIRI sensor are used to discover wildfire hotspots. In the demo you can pose stSPARQL queries to discover information about these hotspots that has been encoded in stRDF. You can also execute refinement operations that increase the occuracy of hotspot information. More information about the complete application can be found in the papers [1], [2].

  2. Semantic classification of scenes in the TerraSAR-X archive of DLR: In this demo we showcase the results of the work on knowledge discovery from satellite images and relevant geospatial datasets done in TELEIOS. In this work the content of patches of images from the DLR TerraSAR-X satellite archive has been determined semi-automatically and it has been captured by a hierarchy of classes modelled as an RDFS ontology. All relevant information has been stored in Strabon and the demo shows ways to correlate it with data from Corine Land Cover, OpenStreetMap and Geonames.

  3. Sextant: Browsing and Mapping the Ocean of Linked Geospatial Data: In this demo we present Sextant, a web-based tool that enables exploration of linked geospatial data as well as creation, sharing, and collaborative editing of thematic maps by combining linked geospatial data and other geospatial information available in standard OGC file formats. More information about Sextant can be found in our recent ESWC demo paper [1].

  4. SexTant: Visualizing Time-Evolving Linked Geospatial Data: In this demo we present the new version of Sextant which adds to the functionality of the previous system the ability to visualize and explore time-evolving linked geospatial data, as well as to edit "temporally-enriched" thematic maps. More information about Sextant can be found in our recent ISWC demo paper [1].

News

Our team will present a tutorial on "ReQuLGD: Representation and Querying for Linked Geospatial Data" at ISWC 2017 in Vienna on October 21st. Don't miss it! Until then, make sure that you check the tutorial page to stay tuned.

Our team will present our work on tools for storing, querying, publishing and visualizing linked geospatial data at FOSS4G-Europe. See you in Paris!

Check out another great MELODIES use-case in which Strabon is used to store and query timeseries data.

Check out a very interesting blog post about using Strabon and Silk to store, query and interlink soil moisture data in the context of the EU project MELODIES.

Our team, in collaboration with CWI gave a tutorial on Publishing and Interlinking Linked Geospatial Data at ESWC 2015.

Our team will present a paper on a Benchmark for Geospatial RDF Stores and a demo on Visualizing Time-Evolving Linked Geospatial Data at ISWC 2013.

Our team won the best demonstration award at ESWC 2013 for Sextant. Check out the demo.

Our team will present a paper on the temporal features of Strabon at ESWC 2013.

Our submission to the Semantic Web Challenge won the third place! Thanks! Check out the real-time fire monitoring operational service.

Our team presented a paper on Strabon, a paper on Querying Linked Geospatial Data with Incomplete Information, a demo paper, an invited demo and our submission to the Semantic Web Challenge at ISWC 2012.

Tutorial on Data Models and Query Languages for Linked Geospatial Data at RW 2012.

Tutorial on Linked Geospatial Data at ESWC 2012.