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Esko Ikkala

Doctoral Candidate, M.Sc. (Tech.)

phone: +358 50 377 0423
email: firstname.lastname@aalto.fi
room: B126 @ Department of Computer Science, Computer Science Building, Konemiehentie 2, Espoo
postal address: Department of Computer Science, P.O. Box 15400, FI-00076 Aalto, Finland

Currently working in the Finnish Ontology Service of Historical Places and Maps project.


Submitted papers

Mikko Koho, Erkki Heino, Petri Leskinen, Minna Tamper, Esko Ikkala, Eetu Mäkelä, Jouni Tuominen and Eero Hyvönen: Linked Open Data and Ontology Infrastructure for Second World War History. Submitted. bib pdf
Data about the Second World War (WW2) is heterogeneous and distributed in different organizations and countries. This paper argues that in order to create aggregated global views of the war, a shared semantic infrastructure is needed, including data models of the real world events, metadata schemas for presenting their documentation, a data harmonization model for data aggregation, and shared domain ontologies for populating the schemas in an interoperable way. As a solution, a Linked Open Data service is presented for publishing data about Finland in WW2. The service is based on W3C Semantic Web standards and best practices, including content negotiation, SPARQL API, download, automatic documentation, and other services supporting re-use of the data. The ontologies and data in the service, totalling ca. 9 million triples, is in use in seven end-user applications of the WarSampo portal, that have had tens of thousands of end-users.


Esko Ikkala, Mikko Koho, Erkki Heino, Petri Leskinen, Eero Hyvönen and Tomi Ahoranta: Prosopographical Views to Finnish WW2 Casualties Through Cemeteries and Linked Open Data. Proceedings of the Workshop on Humanities in the Semantic Web (WHiSe II), CEUR Workshop Proceedings, Vienna, Austria, October, 2017. bib pdf
This paper presents an application for studying the death records of WW2 casualties from a prosopograhical perspective, provided by the various local military cemeteries where the dead were buried. The idea is to provide the end user with a global visual map view on the places in which the casualties were buried as well as with a local historical perspective on what happened to the casualties that lay within a particular cemetery of a village or town. Plenty of data exists about the Second World War (WW2), but the data is typically archived in unconnected, isolated silos in different organizations. This makes it difficult to track down, visualize, and study information that is contained within multiple distinct datasets. In our work, this problem is solved using aggregated Linked Open Data provided by the WarSampo Data Service and SPARQL endpoint.
Petri Leskinen, Mikko Koho, Erkki Heino, Minna Tamper, Esko Ikkala, Jouni Tuominen, Eetu Mäkelä and Eero Hyvönen: Modeling and Using an Actor Ontology of Second World War Military Units and Personnel. Proceedings of the 16th International Semantic Web Conference (ISWC 2017), Springer-Verlag, Vienna, Austria, October, 2017. bib pdf
This paper presents a model for representing historical military personnel and army units, based on large datasets about World War II in Finland. The model is in use in WarSampo data service and semantic portal, which has had tens of thousands of distinct visitors. A key challenge is how to represent ontological changes, since the ranks and units of military personnel, as well as the names and structures of army units change rapidly in wars. This leads to serious problems in both search as well as data linking due to ambiguity and homonymy of names. In our solution, actors are represented in terms of the events they participated in, which facilitates disambiguation of personnel and units in different spatio-temporal contexts. The linked data in the WarSampo Linked Open Data cloud and service has ca. 9 million triples, including actor datasets of ca. 100 000 soldiers and ca. 16 100 army units. To test the model in practice, an application for semantic search and recommending based on data linking was created, where the spatio-temporal life stories of individual soldiers can be reassembled dynamically by linking data from different datasets. An evaluation is presented showing promising results in terms of linking precision
Minna Tamper, Petri Leskinen, Esko Ikkala, Arttu Oksanen, Eetu Mäkelä, Erkki Heino, Jouni Tuominen, Mikko Koho and Eero Hyvönen: AATOS – a Configurable Tool for Automatic Annotation. Proceedings, Language, Technology and Knowledge (LDK 2017), pp. 276-289, Springer-Verlag, Galway, Ireland, June, 2017. bib pdf link
This paper presents an automatic annotation tool AATOS for providing documents with semantic annotations. The tool links entities found from the texts to ontologies defined by the user. The application is highly configurable and can be used with different natural language Finnish texts. The application was developed as a part of WarSampo and Semantic Finlex projects and tested using Kansa Taisteli magazine articles and consolidated Finnish legislation of Semantic Finlex. The quality of the automatic annotation was evaluated by measuring precision and recall against existing manual annotations. The results showed that the quality of the input text, as well as the selection and configuration of the ontologies impacted the results.
Erkki Heino, Minna Tamper, Eetu Mäkelä, Petri Leskinen, Esko Ikkala, Jouni Tuominen, Mikko Koho and Eero Hyvönen: Named Entity Linking in a Complex Domain: Case Second World War History. Proceedings, Language, Technology and Knowledge (LDK 2017), pp. 120-133, Springer-Verlag, Galway, Ireland, June, 2017. bib pdf link
This paper discusses the challenges of applying named entity linking in a rich, complex domain – specifically, the linking of 1) military units, 2) places and 3) people in the context of rich Second World War data. Multiple sub-scenarios are discussed in detail through concrete evaluations, analyzing the problems faced, and the solutions developed. A key contribution of this work is to highlight the heterogeneity of problems and approaches needed even inside a single domain, depending on both the source data as well as the target authority.
Eero Hyvönen, Erkki Heino, Petri Leskinen, Esko Ikkala, Mikko Koho, Minna Tamper, Jouni Tuominen and Eetu Mäkelä: WarSampo: Publishing and Using Linked Open Data about the Second World War. EuropeanaTech Insight, Europeana, 2017. Forth-coming. bib pdf
The article overviews the system WarSampo – Finnish World War 2 on the Semantic Web, the winner of the LODLAM Challenge 2017 Open Data Prize on June 29 in Venice, Italy.


Esko Ikkala: Suomalainen historiallisten paikkojen ja karttojen ontologiapalvelu. MSc Thesis (in Finnish), Aalto University, School of Electrical Engineering, Degree Programme of Automation and Systems Technology, August, 2016. bib pdf
Historiallinen paikkatieto on keskeisessä asemassa muistiorganisaatioiden kokoelmien hallinnassa ja hyödyntämisessä sekä digitaalisten ihmistieteiden tutkimuksessa. Paikkatiedon käsitteleminen muissa kuin erikoistuneissa paikkatietojärjestelmissä sekä paikkatiedon ajallinen ulottuvuus tuovat mukanaan lukuisia haasteita, joihin linkitetyn datan teknologiat ovat tarjonneet lupaavia ratkaisuja. Tässä työssä esitellään kulttuurialan organisaatioiden tarpeeseen kehitetty uusi linkitetyn datan teknologioihin perustuva historiallisten paikkojen ja karttojen palvelumalli, HIPLA. HIPLA-palvelumallin tavoitteena on tarjota yhteinen näkymä eri organisaatioiden hallinnoimaan paikkatietoon ja mahdollistaa hajautettujen paikkatietoaineistojen yhteisöllinen täydentäminen, haku ja selailu sekä nykyisillä että historiallisilla kartoilla. Lisäksi työssä toteutettiin HIPLA-palvelumallin etuja havainnollistava prototyyppisovellus Hipla.fi, jota pilotoitiin osana talvi- ja jatkosodan aineistoja linkitettynä avoimena datana julkaisevaa Sotasampo-projektia. Pilotoinnin tuloksena syntyi talvi- ja jatkosodan paikkaontologia, joka tarjoaa työkalun sotiin liittyvien aineistojen automaattiselle linkitykselle ja aineistojen maantieteelliselle visualisoimiselle.
Esko Ikkala, Jouni Tuominen and Eero Hyvönen: Contextualizing Historical Places in a Gazetteer by Using Historical Maps and Linked Data. Proceedings of Digital Humanities 2016, short papers, pp. 573-577, Kraków, Poland, July, 2016. bib pdf link
Eero Hyvönen, Erkki Heino, Petri Leskinen, Esko Ikkala, Mikko Koho, Minna Tamper, Jouni Tuominen and Eetu Mäkelä: Publishing Second World War History as Linked Data Events on the Semantic Web. Proceedings of Digital Humanities 2016, short papers, pp. 571-573, Kraków, Poland, July, 2016. bib pdf link
Data about wars is typically heterogeneous, distributed in the data silos of the fighting parties, multilingual, and often controversial depending on the political point of view. It is therefore hard for the historians to get a global picture of what has actually happened, to whom, where, when, and how. We argue that Semantic Web and Linked Data technologies are a very promising approach for modeling, harmonizing, and aggregating data about war history. Our goal is to make it possible, for both historians and laymen, to study history in a contextualized way where linked datasets enrich each other. The paper presents the in-use WarSampo 1 system, where massive collections of heterogeneous data about the (Finnish) history of the Second World War are harmonized using an event-based approach, and provided as a Linked Open Data service for applications to use. As a use case, a semantic portal WarSampo providing six different perspectives to the war based on events is presented.
Eero Hyvönen, Erkki Heino, Petri Leskinen, Esko Ikkala, Mikko Koho, Minna Tamper, Jouni Tuominen and Eetu Mäkelä: WarSampo Data Service and Semantic Portal for Publishing Linked Open Data about the Second World War History. The Semantic Web – Latest Advances and New Domains (ESWC 2016) (Harald Sack, Eva Blomqvist, Mathieu d Aquin, Chiara Ghidini, Simone Paolo Ponzetto and Christoph Lange (eds.)), pp. 758-773, Springer-Verlag, May, 2016. bib pdf
This paper presents the WarSampo system for publishing collections of heterogeneous, distributed data about the Second World War on the Semantic Web. WarSampo is based on harmonizing massive datasets using event-based modeling, which makes it possible to enrich datasets semantically with each others’ contents. WarSampo has two components: First, a Linked Open Data (LOD) service WarSampo Data for Digital Humanities (DH) research and for creating applications related to war history. Second, a semanticWarSampo Portal has been created to test and demonstrate the usability of the data service. The WarSampo Portal allows both historians and laymen to study war history and destinies of their family members in the war from different interlinked perspectives. Published in November 2015, theWarSampo Portal had some 20,000 distinct visitors during the first three days, showing that the public has a great interest in this kind of applications.
Eero Hyvönen, Esko Ikkala and Jouni Tuominen: Linked Data Brokering Service for Historical Places and Maps. Proceedings of the 1st Workshop on Humanities in the Semantic Web (WHiSe), pp. 39-52, CEUR Workshop Proceedings, Heraklion, Crete, Greece, May, 2016. Vol 1608. bib pdf link
This paper presents a new Linked Open Data brokering service model HIPLA for using and maintaining historical place gazetteers and maps based on distributed SPARQL endpoints. The model introduces several novelties: First, the service facilitates collaborative maintenance of geo-ontologies and maps in real time as a side effect of annotating contents in legacy cataloging systems. The idea is to support a collaborative ecosystem of curators that creates and maintains data about historical places and maps in a sustainable way. Second, in order to foster understanding of historical places, the places can be provided on both modern and historical maps, and with additional contextual Linked Data attached. Third, since data about historical places is typically maintained by different authorities and in different countries, the service can be used and extended in a federated fashion, by including new distributed SPARQL endpoints (or other web services with a suitable API) into the system. To test and demonstrate the model, we created the first prototype implementation Hipla.fi of the HIPLA model. Hipla.fi is based on four Finnish datasets in SPARQL endpoints totaling some 840,000 geocoded places on 450 historical maps from two atlas series aligned on modern maps, and on the Getty Thesaurus of Geographic Names (TGN) SPARQL endpoint in the US. As a first application, a part of the Hipla.fi data service has been applied in creating a 5 million triple semantic portal of historical Second World War data with tens of thousands of end users.


Eero Hyvönen, Jouni Tuominen, Eetu Mäkelä, Jérémie Dutruit, Kasper Apajalahti, Erkki Heino, Petri Leskinen and Esko Ikkala: Second World War on the Semantic Web: The WarSampo Project and Semantic Portal. Proceedings of the ISWC 2015 Posters & Demonstrations Track, CEUR-WS Proceedings, Bethlehem, PA, USA, October, 2015. Vol 1486. bib pdf link
This paper initiates and fosters work on publishing Linked Open Data about the Second World War. It is argued that the heterogeneous, distributed data about the international world war history makes a promising use case for semantic technologies. We hope that by making war data openly available we can learn from the past and promote peace.
Eero Hyvönen, Jouni Tuominen, Esko Ikkala and Eetu Mäkelä: Ontology Services Based on Crowdsourcing: Case National Gazetteer of Historical Places. Proceedings of the ISWC 2015 Posters & Demonstrations Track, CEUR-WS Proceedings, Bethlehem, PA, USA, October, 2015. Vol 1486. bib pdf link
This paper introduces the idea of applying crowdsourcing to evolving ontology services; the goal is to facilitate collaborative maintenance of ontologies in real time as a side effect of annotating contents in legacy cataloging systems. The idea is being implemented in the use case of creating and managing a national level gazetteer of historical places in Finland.


Esko Ikkala, Eetu Mäkelä and Eero Hyvönen: TourRDF: Representing, Enriching, and Publishing Curated Tours Based on Linked Data. 19th International Conference of Knowledge Engineering and Management (EKAW 2014), Demo and Poster Papers, November, 2014. bib pdf
Current mobile tourist guide systems are developed and used in separate data silos: each system and vendor tends to use its own proprietary, closed formats for representing tours and point of interest (POI) content. As a result, tour data cannot be enriched from other providers’ tour and POI repositories, or from other external data sources — even when such data were publicly available by, e.g., cities willing to promote tourism. This paper argues, that an open shared RDF-based tour vocabulary is needed to address these problems, and introduces such a model, TourRDF, extending the earlier TourML schema into the era of Linked Data. As a test and an evaluation of the approach, a case study based on data about the Unesco World Heritage site Suomenlinna fortress is presented.
Eero Hyvönen, Miika Alonen, Esko Ikkala and Eetu Mäkelä: Life Stories as Event-based Linked Data: Case Semantic National Biography. Proceedings of ISWC 2014 Posters & Demonstrations Track, CEUR Workshop Proceedings, October, 2014. bib pdf link
This paper argues, by presenting a case study and a demonstration on the web, that biographies make a promising application case of Linked Data: the reading experience can be enhanced by enriching the biographies with additional life time events, by proving the user with a spatio-temporal context for reading, and by linking the text to additional contents in related datasets.

(total: 15 publications)

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