Arkiv för kategorin 'PhD defence'

Valentina Ivanova defended her PhD thesis on Fostering User Involvement in Ontology Alignment and Alignment Evaluation

Postad i kategorin: PhD defence den 13 February, 2018

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On January 26, our PhD candidate Valentina Ivanova defended successfully her thesis with the title “Fostering User Involvement in Ontology Alignment and Alignment Evaluation.”
This thesis focuses on supporting users during the cognitively intensive ontology alignment process and makes several contributions.

First, front- and back-end system features that foster user involvement during the alignment process were identified and their support has been investigated in existing systems Then this was further narrowed down to investigate features in connection to manual validation while also considering the level of user expertise by assessing the impact of user errors on alignments’ quality. As developing and aligning ontologies is an error-prone task, there is also an investigation on the benefits of the integration of ontology alignment and debugging.
Further, interactive comparative exploration and evaluation of multiple alignments at different levels of detail was enabled by developing a dedicated visual environment—Alignment Cubes—which allows for alignments’ evaluation even in the absence of reference alignments.
Finally, inspired by the latest technological advances three promising directions for the application of large, high-resolution displays in the field were identified: improving the navigation in the ontologies and their alignments, supporting reasoning and collaboration between users.

Valentina’s work on the thesis was supervised by Patrick Lambrix, and co-supervised by Nahid Shahmehri. The opponent was Fabien Gandon from INRIA, France. The examination committee consisted of Oscar Corcho from Universidad Politecnica de Madrid, Mathieu d’ Aquin from the National University of Ireland Galway and Claes Lundström from Sectra and Linköping University. Mattias Arvola from Linköping University was backup examination committee member.

Find the thesis in the Diva portal.


Karl Hammar defended his PhD thesis on Ontology Design Patterns

Postad i kategorin: Ontology Design Patterns, PhD defence den 22 October, 2017

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On September 29, Karl Hammar successfully defended his PhD thesis entitled “Content Ontology Design Patterns: Qualities, Methods, and Tools”. The thesis was first presented by the opponent, professor Harald Sack, FIZ, Karlsruhe, Germany, who then continued to discuss the research results and future ideas with Karl. The three members of the examining committee then continued the discussion with Karl, before unanimously deciding to approve his thesis and award the PhD degree to Karl. At which point we could all congratulate him to a an interesting defence and an excellent thesis. In particular, his three supervisors, Henrik Eriksson (LiU), Eva Blomqvist (LiU) and Vladimir Tarassov (JTH) were of course the first to congratulate him, followed by colleagues and family.

Karl Hammar’s research has aimed to combine quantitative and qualitative research methods, primarily based on five ontology engineering projects involving inexperienced ontologists, studying how Ontology Design Patterns (ODPs) can support that specific group of users. A series of ontology engineering workshops and surveys provided data about developer preferences regarding ODP features and quality, ODP usage methodology, and ODP tooling needs. Other data sources were ontologies and ODPs published on the web, which have been studied in detail. To evaluate tooling improvements, experimental approaches provided data from comparison of new tools and techniques against established alternatives.

The analysis of the gathered data resulted in a set of measurable quality indicators that cover aspects of ODP documentation, formal representation or axiomatisation, and usage by ontologists. These indicators highlight quality trade-offs: for instance, between ODP Learnability and Reusability, or between Functional Suitability and Performance Efficiency. These are things that ontology engineers need to keep in mind when using ODPs in their ontologies, and in particular if they are inexperienced ontologists. Furthermore, the results demonstrated a need for ODP tools that support three novel property specialisation strategies, and highlighted the preference of inexperienced developers for template-based ODP instantiation, neither of which were supported in prior tooling. The studies also resulted in improvements to ODP search engines based on ODP-specific attributes. Finally, the analysis showed that a specific ontology engineering methodology, the eXtreme Design (XD), should include guidance for developer roles and responsibilities in ontology engineering projects, suggestions on how to reuse existing ontology resources, and approaches for adapting XD to project-specific contexts. Karl therefore proposed a new version of the XD methodology, specifically covering these aspects.

The thesis can be found here.








Congratulations Karl!


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Zlatan Dragisic defended his PhD Thesis on Completion of Ontologies and Ontology Networks

Postad i kategorin: PhD defence den 27 September, 2017

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Yesterday, on September 26, our PhD candidate Zlatan Dragisic defended successfully his thesis with the title “Completion of Ontologies and Ontology Networks.” The thesis makes several contributions: First, the problem of completing the is-a structure in ontologies is formalized as an abductive reasoning problem and the thesis introduces algorithms as well as systems for dealing with the problem. Regarding the completion of alignments between ontologies, the thesis provides a performance study of systems that participated in the Ontology Alignment Evaluation Initiative, and an approach to reduce the search space when generating such alignments. Next, the thesis reports a broad study of state-of-the-art ontology alignment systems in terms of user involvement during the completion process and, in particular, the impact of user errors in this process. Finally, the thesis introduces an approach to integrate ontology completion and ontology alignment into an existing ontology development methodology.

Zlatan’s work on the thesis was supervised by Patrick Lambrix, and co-supervised by Nahid Shahmehri, Marco Kuhlmann, and Fang Wei-Kleiner. The opponent was Erhard Rahm from the University of Leipzig, Germany. The examination committee consisted of Asuncion Gomez-Perez from Universidad Politecnica de Madrid, Jerome Euzenat from INRIA and Graham Kemp from Chalmers University of Technology. Magnus Bång from Linköping University was backup examination committee member.

Find the thesis in the Diva portal.

Well done Zlatan! Congratulations!


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Semantic Web research at LiU

The Semantic Web is an extension of the traditional Web towards having machine processable content and interlinked data on the Web, with well-described semantics.

Ideally we would be able to view the whole Web as a large set of interconnected databases, which can be queried and browsed by software systems as well as human users. Semantic Web research at LiU includes areas such as ontologies and ontology engineering (ontology design patterns, ontology alignment and completion, ontology and alignment visualisation), graph databases and triple stores, querying the Web of data, RDF stream processing and complex event processing, as well as applications of these technologies in a number of fields, including open data, security, decision support systems, e-health and e-science, etc.

The aim of this blog is to report on the activities of our research group, and make results accessible to a wider audience.

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