Welcome to the page of our team!
Knowledge Representation, Reasoning and Analytics


None of us is as smart as all of us

Our team belongs to the Management of Data, Information and Knowledge Group (MaDgIK) of the Department of Informatics and Telecommunications of the National and Kapodistrian University of Athens. Our work focuses on various aspects of knowledge harvesting, representation, reasoning and analytics and it is done under the supervision of Professor Manolis Koubarakis.

The present web pages present our recent research and development activities. During the past few years, we have developed state-of-the-art technologies and tools for managing, processing, interlinking and visualizing big linked geospatial and temporal data. More specifically, we have worked on:

  • Extending RDF and SPARQL for querying geospatial and temporal data
  • Question answering techniques for knowledge graphs with geospatial and temporal knowledge
  • Extracting knowledge from Earth Observation data
  • Converting data from arbitrary geospatial formats (e.g., shapefiles, KML, geospatial databases) into RDF
  • Storing and querying linked geospatial and temporal data, using stSPARQL/GeoSPARQL
  • Connecting to existing geospatial databases and posing GeoSPARQL queries on-the-fly using ontologies and mappings without data materialization into RDF
  • Creating spatial and temporal links between entities from different data sources
  • Visualization of linked geospatial and temporal data
  • Publishing various European data sets as linked data

The above technological innovations have been deployed in many applications dealing with Earth Observation data e.g., data from the Sentinel satellites of the European Copernicus program.

Another recent contribution of our team is the representation and querying of legislation using ontologies and linked data. The system Nomothesi@ we have developed harvests Greek legislation from the National Printing Office and makes it available on the Web as linked data so it can be linked to other publicly available Greek open data to develop interesting applications for the public or the legal profession.

These efforts have been funded by the European research projects TELEIOS, LEO, Optique, Melodies, Big Data Europe, WDAqua, Copernicus App Lab and the research excellence grant SCARE from the Greek General Secretariat for Research and Technology. All our tools are state-of-the-art and we are constantly maintaining and enchancing them with new features. So stay tuned!


Open source tools to navigate the world of data and create knowledge from it


GeoTriples is a tool for transforming geospatial data from their original formats (e.g., shapefiles or spatially-enabled relational databases) into RDF.


Strabon is a spatiotemporal RDF store. You can use it to store linked geospatial data that changes over time and pose queries using two popular extensions of SPARQL (GeoSPARQL and stSPARQL). Strabon has been shown experimentally to be the most efficient spatiotemporal RDF store available today.


Do you want to get the most of your relational data combining them with linked geospatial data without converting them to RDF? No problem. Ontop-spatial can create virtual geospatial RDF graphs on top of your geospatial databases.


Silk is an open source framework for integrating heterogeneous data sources. We have extended the tool to allow the discovery of spatial and temporal links among datasets. This extra functionality is now part of the default distribution.


Sextant is a web based and mobile ready platform for visualizing, exploring and interacting with linked geospatial data. The core feature of Sextant is the ability to create thematic maps by combining geospatial and temporal information that exists in a number of heterogeneous data sources.


JedAI constitutes an open source, high scalability toolkit that offers out-of-the-box solutions for any data integration task, e.g., Record Linkage, Entity Resolution and Link Discovery. At its core lies a set of domain-independent, state-of-the-art techniques that apply to both RDF and relational data. These techniques rely on an approximate, schema-agnostic functionality based on (meta-)blocking for high scalability.


My powers are ordinary. Only my application brings me success


We would like to give to ordinary citizens, software developers and legal professionals the ability to have at their fingertips advanced ways of searching and understanding legislation. We showcase this by harvesting Greek legislation from the National Printing Office, making it available as linked data and interlinking with other open Greek data sets.

Change Detection from Remote Sensing and Social Media Sources

The change detection application is realized by two workflows. The change detection workflow uses satellite images to detect areas with changes in land cover or land use. The event detection workflow works in the opposite direction: it is triggered by news and social media information about important events.


It is the supreme art of the teacher to awaken joy in creative expression and knowledge

We often present our work in tutorials that take place at international conferences. Some recent tutorials are the following:


Projects which have funded our work

Our Team

The strength of the team is each individual member. The strength of each member is the team.

Manolis Koubarakis


Konstantina Bereta

Research Assistant, PhD student

Dimitris Bilidas

Research Assistant, PhD student

George Stamoulis

Research Assistant, PhD student

George Argyriou

Research Assistant, MSc student

Dharmen Punjani

Research Assistant, PhD student

Despina-Athanasia Pantazi

Research Assistant, MSc student

Nikolaos Karalis

Research Assistant, MSc student

Theofilos Ioannidis

Research Assistant, PhD student

Iosif Angelidis

Research Assistant, MSc student

Former Members

Kostis Kyzirakos

Charalampos Nikolaou

Manos Karpathiotakis

George Garbis

Stella Giannakopoulou

Panayiotis Smeros

Ioannis Vlachopoulos

Kalliroi Dogani

Maria Karpathiotaki

Dimitrianos Savva

Manos Thanos

George Papadakis

Efi Karra