short biography
Pavlos Fafalios

Welcome to my personal Web page!

I am currently a postdoctoral researcher at L3S Research Center (Leibniz University of Hanover, Germany), working on methods for the the semantic and entity-based exploration of Web and Social Media archives (in the context of the Alexandria ERC project). Before joining L3S, I was a research assistant at the Information Systems Laboratory of FORTH-ICS. I obtained my PhD from the Computer Science Department of University of Crete (Greece) in 2016.

My main research interests fall in the following areas: Information Retrieval, Exploratory and Semantic Search, Data Mining, Semantic Web and Linked Data. I am also very interested in Conceptual Modeling and Knowledge Representation.

The results of my research have been published in more than 30 international (peer-reviewed) journals, conferences, and workshops.

You can find detailed information in my Curriculum Vitae (last update: July 12, 2018) (ελληνική έκδοση).

P. Fafalios, V. Iosifidis, K. Stefanidis, and E. Ntoutsi,
Tracking the History and Evolution of Entities: Entity-centric Temporal Analysis of Large Social Media Archives,
P. Fafalios, H. Holzmann, V. Kasturia, and W. Nejdl,
Building and Querying Semantic Layers for Web Archives (Extended Version),
M. Quraishi, P. Fafalios, and E. Herder,
Viewpoint Discovery and Understanding in Social Networks,
10th International ACM Web Science Conference (WebSci'18), Amsterdam, The Netherlands, May 27-30, 2018.
P. Fafalios, V. Kasturia, and W. Nejdl,
Ranking Archived Documents for Structured Queries on Semantic Layers,
2018 ACM/IEEE-CS Joint Conference on Digital Libraries (JCDL'18), Fort Worth (Texas, USA), June 3-6, 2018.
P. Fafalios, V. Iosifidis, E. Ntoutsi, and S. Dietze,
TweetsKB: A Public and Large-Scale RDF Corpus of Annotated Tweets,
15th Extended Semantic Web Conference (ESWC'18), Heraklion, Crete, Greece, June 3-7, 2018.
Nominated for the "Best Resource Paper" award!
N. Mohapatra, V. Iosifidis, A. Ekbal, S. Dietze, and P. Fafalios,
Time-Aware and Corpus-Specific Entity Relatedness,
Workshop on Deep Learning for Knowledge Graphs and Semantic Technologies (DL4KGS), in conjunction with the 15th Extended Semantic Web Conference (ESWC'18), Heraklion, Crete, Greece, June 3-7, 2018.
T. Yannakis, P. Fafalios, and Y. Tzitzikas,
Heuristics-based Query Reordering for Federated Queries in SPARQL 1.1 and SPARQL-LD,
2nd Workshop on Querying the Web of Data (QuWeDa), in conjunction with the 15th Extended Semantic Web Conference (ESWC'18), Heraklion, Crete, Greece, June 3-7, 2018.
M. Mountantonakis, N. Minadakis, Y. Marketakis, P. Fafalios and Y. Tzitzikas
Connectivity, Value and Evolution of a Semantic Warehouse,
2017 show
2016 show
2015 show
2014 show
2013 show
2012 show
2011 show
projects involved top
Alexandria (2016 - now)

The ALEXANDRIA project (ERC Nr. 339233) aims to develop models, tools and techniques necessary to explore and analyze Web archives in a meaningful way. ALEXANDRIA will significantly advance semantic and time-based indexing for Web archives using human-compiled knowledge available on the Web, to efficiently index, retrieve and explore information about entities and events from the past. For more information visit:

Role: Research on methods for the semantic and entity-based exploration of Web Archives.

BlueBRIDGE (2015 - 2016)

European initiative funded under the H2020 framework to further develop and exploit the iMarine e-Infrastructure data services for an ecosystem approach to fisheries. For more information visit:

Role: I extended the system X-Search for enabling the stochastic re-ranking of search results based on extracted entities. Moreover, I participated in the study of methods for quantifying the connectivity and evolution of a semantic warehouse.

iMarine (2012 - 2014)

iMarine (Data e-Infrastructure Initiative for Fisheries Management and Conservation of Marine Living Resources) is a European Commission funded project that kicked-off on 1st Nov 2011. It is an open and collaborative initiative that will establish a data infrastructure to support the Ecosystem Approach to fisheries management and conservation of marine living resources. For more information visit:

Role: I designed and developed the system X-Search for the semantic exploration of search results, as well as the system X-Link for the extraction of entities and their further enrichment by exploiting Linked Data. Moreover, I participated in the development of the top-level ontology "MarineTLO" which allows describing and integrating marine data.

PerFedPat (2012 - 2016)

The PerFedPat project (funded by FP7/Research Executive Agency) aims to research into a new generation of advanced patent search systems for the patent related industries and the whole spectrum of patent users by designing a new exciting framework for integrating multiple patent data sources, patent search tools and UIs. For more information visit:

Role: I collaborated with Professor Michail Salampasis for the exploitation of the results of my PhD studies in the context of Patent Search. Specifically, I studied methods on how to enrich patent search results with static and dynamically-mined metadata for enabling exploratory patent searching.

MUMIA (2012 - 2014)

Multilingual and Multifaceted Interactive Information Access (MUMIA), COST Action IC1002. The main objective of the Action is to coordinate and support the interaction and harmonization of high quality research at a European level in the field of multilingual and multifaceted interactive information access with a view to contribute to the development of next-generation search systems. For more information visit:

Role: Member of the action, participation to working groups and management committee meetings, involved in WG4 (Semantic Search, Faceted Search and Visualization).

software top
SPARQL-LD is an extension of SPARQL 1.1 that enables to directly fetch and query RDF data from heterogeneous sources via SERVICE calls. A distinctive characteristic of SPARQL-LD is that it allows querying and integrating even data in datasets returned by a portion of the query, i.e. identified at query-execution time. You can find more information (and try it) here. The source code is available on GitHub.
X-Search is a web search service that reads the description of an underlying search source, and is able to query that source and analyze in various ways the returned results. X-Search also exploits the availability of semantic repositories. You can try X-Search (and find more information) here.
X-Link is a fully configurable, Linked Data-based, named entity extraction tool. X-Link is capable to a) identify entities of interests (e.g. persons, locations, organizations, etc.) in any type of document, b) link the identified entities with semantic resources (i.e. with URIs), c) enrich the identified entities with semantic information (i.e. with properties and related entities), and d) infer whether and how the identified entities are associated. The main strength of X-Link is its extensive configurability: the user/administrator/developer can define and update the categories of entities that are interesting for the application at hand by exploiting one or more (on-line) Semantic Knowledge Bases. The user is also able to specify how to link the identified entities with semantic resources and how to enrich them with more information. You can find more information here.
IOS (Instant Overview Search) is a search-as-you-type functionality for web searching which provides an overview of the results as the user types his query letter-by-letter. You can try IOS (and find more information) here.
Theophrastus is a system that supports the automatic annotation of web documents through entity mining and provides exploration services by exploiting Linked Open Data (LOD), in real-time and only when needed. Theophrastus was awarded the 1st prize in Blue Hackathon 2013. You can find more information (and try it) here.
Ithaca is a tool that reads open datasets, converts their data to RDF triples and loads the derived triples in a Virtuoso warehouse, offering thereby an API for directly exploiting the underlying data. Ithaca was awarded the 1st prize in Hack4Med 2014 (the HOMER project Hackathon). The source code is available on GitHub.
SPARQL Endpoint Browser
A web application for browsing the content of a SPARQL endpoint. You can try it here.
work/research experience top
June 2016 - now
Postdoctoral Researcher
L3S Research Center, University of Hannover, Germany.
December 2010 - May 2016
Research assistant, software engineer, graduate fellow
Information Systems Laboratory (ISL), Institute of Computer Science (ICS),
Foundation for Research and Technology - Hellas (FORTH), Heraklion, Greece.
my education top
October 2012 - May 2016
Ph. D.
Computer Science Department, University of Crete, Greece
Thesis Topic: "Exploiting Linked Data in Exploratory Search"
Thesis Supervisor: Ass. Prof. Yannis Tzitzikas
2010 - 2012
M. Sc. in Information Systems and E-commerce Technologies
Computer Science Department, University of Crete, Greece
Thesis Topic: "Indexes and Algorithms for Scalable and Flexible Instant Overview Search" [slides]
Thesis Supervisor: Ass. Prof. Yannis Tzitzikas
2003 - 2009
Dipl. Eng. in Information and Communication Systems Engineering
Department of Information and Communication Systems Engineering, School of Engineering, University of the Aegean, Greece
Thesis Topic: "Meta-Seeker: a Retroactive Algorithm for Personalizing Information from Multiple Web Search Services"
Thesis Supervisor: Ass. Prof. Ioannis Anagnostopoulos
training/summer schools
1st KEYSTONE Training School on "Keyword Search over Big Data".
July 20-24, 2015, Malta
3rd Multilingual and Multifaceted Interactive Information Access (MUMIA) Training School
on "Information Retrieval and Interactive Information Access",
July 21-25, 2014, Heraklion, Crete, Greece
1st Multilingual and Multifaceted Interactive Information Access (MUMIA) Training School
on "Building Next Generation Search Systems",
September 24-28, 2012, Olympiada, Chalkidiki, Greece
2nd Summer School on "Service and Software Architectures, Infrastructures and Engineering (SSAIE)",
June 28 - July 2, 2010, Heraklion, Crete, Greece
awards and distinctions top
Fellowship from legacy "Maria Michael Manasaki" for the academic year 2014-2015. This fellowship is awarded once a year to the one or two best graduate students of Computer Science department of University of Crete.
1st prize for the "Best Homer Federation Open Data reuse app", 2nd prize for the "Most useful application for a public sector administration", and 1st prize for the “Best Solution for Crete”, in Hack4Med, the HOMER project Hackathon, held in the University of Crete, Department of Computer Science, 16-17 May 2014, Voutes Campus, Heraklion, Greece. Michalis Mountantonakis and I developed and presented the system "Ithaca: From Open Data to Linked Open Data".
1st prize in Blue Hackathon 2013, held in the Hellenic Centre for Marine Research (HCMR), 1-2 July 2013, Gournes, Heraklion, Greece. Panagiotis Papadakos and I developed and presented the system "Theophrastus: A Semantic Exploration Tool for Marine Taxonomists".
some personal information top

I was born in Chios, a beautiful island at the east of Greece, just five miles off the Asia Minor coast. I grew up there with my parents, my sister Nantia, my grandparents, and a lot of friends. In September 2003, I moved a few miles souther to Samos island where I lived 5 very beautiful years studying Information and Communication Systems. In November 2008 I joined the Greek Army Forces for one year to accomplish my military service. In February 2010 I started my graduate studies in Crete island (specifically in Heraklion city) where I lived 6 wonderful years. In June 2016 I moved to Hannover (Lower Saxony, Germany) where I live until now.

In my free time, I like spending time with friends, watching and playing sports, traveling around, watching movies, reading books, and taking photos (you can find some here).

contact me top
email: fafalios[at]l3s[dot]de
gmail: fafalios.pavlos
skype: pavlos098
google scholar