Completing the Is-a Structure in Description Logics Ontologies
Zlatan Dragisic · Linköping University Electronic Press eBooks · 2014
The World Wide Web contains large amounts of data and in most cases this data is without any explicit structure.The lack of structure makes it difficult for automated agents to understand and use such data.A step towards a more structured World Wide Web is the idea of the Semantic Web which aims at introducing semantics to data on the World Wide Web.One of the key technologies in this endeavour are ontologies which provide means for modeling a domain of interest.Developing and maintaining ontologies is not an easy task and it is often the case that defects are introduced into ontologies.This can be a problem for semanticallyenabled applications such as ontology-based querying.Defects in ontologies directly influence the quality of the results of such applications as correct results can be missed and wrong results can be returned.This thesis considers one type of defects in ontologies, namely the problem of completing the is-a structure in ontologies represented in description logics.We focus on two variants of description logics, the EL family and ALC, which are often used in practice.This work has been supported by the Swedish National Graduate School of Computer Science (CUGS), the Swedish e-Science Research Center (SeRC) and Vetenskapsrådet (VR).iii At the beginning of my PhD studies this moment, even though half-way, seemed as a distant dream.The journey to this point was not easy and was full of ups and downs.However, the first half of the way is at its end and this thesis would not be possible without the help and support of a number of people along the way.I would like to express my sincere gratitude to my supervisor Professor Patrick Lambrix for providing me with an opportunity to work on this project and all the guidance, help and advice given along the way.This made me improve and become better in what I am doing.Thank you for your patience and encouragement, especially in times when it seemed that things were not going my way.I am extremely grateful to my secondary supervisors, Professor Nahid Shahmehri and Assistant Professor Fang Wei-Kleiner.Thank you for all the comments and discussions raised during our meetings which gave me a different perspective on my work and immensely improved it together with my critical thinking.To all the former and current colleagues at ADIT I give my sincere thanks for making the work environment more enjoyable.I thank you for all lunches, discussions and various activities.They might not have always been productive but they raised some interesting questions about life, the universe and everything.I am also thankful to all the administrative staff, especially Anne, Eva, Inger, Karin and Marie