Picture of Olaf Hartig Olaf Hartig
Associate Professor (Universitetslektor, docent)
Division for Database and Information Techniques
Department of Computer and Information Science (IDA)
Linköping University

View Olaf Hartig's profile on Google Scholar   View Olaf Hartig's profile on DBLP   Olaf Hartig's Blog   View Olaf Hartig's profile on Github   View Olaf Hartig's profile on Twitter   View Olaf Hartig's profile on Slideshare   View Olaf Hartig's profile on videolectures.net


Feb. 23, 2019: I have defined an approach to specify schemas for Property Graphs by using the GraphQL schema definition language.

Feb. 15, 2019: Together with Ruben Taelman, we have got a tutorial accepted at the 18th International Semantic Web Conference (ISWC). The title of the tutorial is "An Introduction to GraphQL."

October 8, 2018: It's done!! I have successfully delivered my Docent lecture today! This was the last step to being awarded the title Docent. (If you are not familiar with the academic system in Sweden: Docent is an academic degree at a level similar to Habilitation in other European countries.)

October 3, 2018: Request for feedback: We aim to develop a performance benchmark for GraphQL server implementations and we seek feedback on our first design artifact, that is, a description of so-called "choke points" that the benchmark will be designed to test. Please find the PDF file description on Github and share your feedback.

September 13, 2018: We have won the best paper award for our paper titled "CostFed: Cost-Based Query Optimization for SPARQL Endpoint Federation" at the SEMANTiCS Conference 2018. This is joint work with Muhammad Saleem, Alexander Potocki, Tommaso Soru (all University of Leipzig) and Axel-Cyrille Ngonga Ngomo (University of Paderborn). We have made available a PDF file preprint of this paper.

August 8, 2018: I published a PDF file lightweight high-level summary of our research paper about the "Semantics and Complexity of GraphQL" (PDF file preprint).

July 2, 2018: My talk about "Fundamental Properties of the GraphQL Language" at GraphQL Europe 2018 has been videotaped. You can find the recording at Youtube.

May 23, 2018: I will have the honor to serve as a research track co-chair of the 18th International Semantic Web Conference, ISWC 2019, which will take place in Auckland at the end of October 2019. Additionally, I will serve as a co-chair of the posters and demos track of the 16th European Semantic Web Conference, ESWC 2019.

May 3, 2018: I have made available a PDF file preprint of our IJCAI 2018 paper titled "A Model of Distributed Query Computation in Client-Server Scenarios on the Semantic Web." Note that this paper is an abridged version of our ISWC 2017 best research paper (preprint), which has been invited to the Sister Conference Best-Paper Track at the 27th International Joint Conference on Artificial Intelligence (IJCAI). The conference will take place in July in Stockholm.

Research Interests

I am interested in problems related to the management of data and databases. My focus in this broad context is on data on the Web (Semantic Web and Linked Data, in particular) and on graph data, as well as on problems in which the data is distributed over multiple, autonomous and/or heterogeneous sources (keyword: federated data management). Other keywords that appear in some of my work are data provenance and data quality. Regarding all of these topics, my interests range from systems-building related research (e.g., efficient storage of datasets and databases, query processing, and query optimization) all the way to theoretical foundations (e.g., complexity and expressive power of query languages).


Here is my academic CV: PDF file

Selected Publications

This following list contains selected publications. There is also a complete list of all my publications.

Program Committees

Additional Activities


Ongoing and upcoming courses at LiU for which I am the course leader:

Earlier courses at LiU for which I was the course leader:

Other courses at LiU that I am or was involved in:

Earlier courses at UWaterloo for which I was the course leader:

Earlier practicals and seminars at HU Berlin for which I was responsible as a teaching assistant: