Harm Delva

About me

I am a PhD student at IDLab, affiliated with both Ghent University and imec. My original research subject lay at the intersection of the Semantic Web technologies and Linked Open Data publishing, but with a focus on researching how applications can find and use this data - beyond the traditional SPARQL usecase. I have worked on a flexible and multi-modal route planner, as well as an autocompletion client that can query several heterogeneous data sources at the same time. Our route planner is able to find subjectively pleasant routes by asking the user what they want to see while walking; see it in action here. And, because all computations are done on the client, there are no data-hoarding behemoths that are learning your opinions on shopping streets.

Other than that, I have developed an appreciation for the intricacies of Geographic Information Systems (GIS), especially for Volunteered Geographic Information (VGI) projects such as OpenStreetmap and, closer to home, Telraam. Of course, it is not enough to simply publish Open Data: people must be able to find this data. Whenever time permits it, I like to work on making data discoverable, and try to follow the developments within the FAIR community. Alternatively, I would like to help pave the way towards more mature WebAssembly tooling for working with RDF data — my applications have a need for speed.

Last, but not least, I would love to explore Semantic Web applications that focus on pen-and-paper games, such as as Dungeons & Dragons. Why spend years modelling and gathering data from the real world, when there are perfectly suitably imaginary worlds out there? By avoiding pedantic discussions (what is an address really?), we could skip straight to the good stuff such as semantic interoperability.
Curious to hear what I have in mind? Feel free to reach out, I will always find time to discuss this.

Professional Experience

IDLab, Ghent University - imec Ghent, Belgium

PhD Researcher March 2019 -
- Member of the KNowledge On Web Scale research group which focuses on the generation, publication, and querying of Knowlegde Graphs on the Web;
- Within our research group, I focus on semantically annotating datasets and Web APIs to optimize their discoverability and reuse potential;
- Developed a prototype of a multi-modal route planning application that runs entirely on Linked Data Fragments;
- Investigated how IoT data from the NGSI-LD ecosystem can be publicly disclosed, while retaining compliancy to standards such as the OSLO standards defined by the Flemish government;
- Provided consultancy services for companies that are interested in knowledge graphs and Open Data.
Trackuity Ghent, Belgium

Data Scientist July 2017 - February 2019
- Developed recommender systems and targeted advertisements for classified sites in Europe and Latin America;
- Performed data analytics to identify shortcomings in our service, and set up A/B tests for possible improvements;
- Set up ETL pipelines for dozens of clients, as we often extracted and sanitized all the clients' data ourselves;
- Conceived and developed prototypes for two new products from start to finish.
Trackuity Ghent, Belgium

Internship December 2016
- Researched, implemented, and compared the state-of-the-art of latent factor models in recommender systems;
- Wrote a technical report in fulfilment of a research grant.
Ghent University Ghent, Belgium

Student Job June 2016 - July 2016
- Developed the foundations of the Dodona platform, which students use to submit programming exercises and receive immediate feedback;
- Encapsulated the existing Python code evaluators in Docker containers;
- Set up the communication between the web server and the Docker containers.

Additional Academic Experience

Assisted with the practical sessions for the Programming, Web Development and Big Data Science courses at Ghent University.

Mentored Master Thesises:

Jeroen Flipts. Fragmenting Public Transport Timetables On the Web In Tiles for Serverless Route Planning. 2020.

Thomas Neuser. Een Routeplanner Op Basis Van Open Data: Hoe Hypermedia Controls De Semantische Beschrijving Van Datasets In Planner.js Kunnen Verbeteren. 2020.

Pieter-Jan Vandenberghe. Designing a Web Interface for Scalable Public Transport Routing Through Spatiotemporal Fragmentation of Public Transport Networks. 2019.

Tim Vanhee. Studying the Technique of Contraction Hierarchies for Routing On Web-scale. 2019.

Program committee member at WSDM 2020, SIGIR 2020, SIGIR 2021

Publications

2020

Interactive Route Personalization Using Regions of Interest

Harm Delva, Annelien Smets, Pieter Colpaert, Pieter Ballon, Ruben Verborgh

Proceedings of the 2nd International Workshop on Semantics for Transport

pdf html slides demo
How to Prototype a Client-Side Route Planner for Helsinki with Routable Tiles and Linked Connections

Julián Andrés Rojas, Harm Delva, Pieter Colpaert, Ruben Verborgh

Proceedings of the 2nd International Workshop on Semantics for Transport

pdf
Geospatial Partitioning of Open Transit Data

Harm Delva, Julián Andrés Rojas, Pieter-Jan Vandenberghe, Pieter Colpaert, Ruben Verborgh

International Conference on Web Engineering

Winner of Best Student Paper Award

pdf html slides
Efficient Live Public Transport Data Sharing for Route Planning on the Web

Julián Andrés Rojas, Dylan Van Assche, Harm Delva, Pieter Colpaert, Ruben Verborgh

International Conference on Web Engineering
html

2019

Client-side route planning: preprocessing the OpenStreetMap road network for Routable Tiles

Harm Delva, Julian Andres Rojas Melendez, Ben Abelshausen, Pieter Colpaert, Ruben Verborgh

Academic Track, State of the Map 2019

pdf slides demo
Decentralized Publication and Consumption of Transfer Footpaths

Harm Delva, Julian Andres Rojas Melendez, Pieter Colpaert, Ruben Verborgh

First International Workshop on Semantics for Transport

pdf html slides
Republishing OpenStreetMap’s roads as Linked Routable Tiles

Pieter Colpaert, Ben Abelshausen, Julián Andrés Rojas Meléndez, Harm Delva, Ruben Verborgh

European Semantic Web Conference

pdf html demo

Projects

A client-side route planner that uses Linked Data Fragments to compute routes just the way you like them. My own contributions here have been to optimize the route planner to be competive with server-side alternatives. Computing long routes isn't entirely there yet, but it's definitely useable for city-level routes. Have a look at our Regions of Interest demo for example, where you can tweak a walk through the city of Ghent to your heart's content. Or if you want to see how longer routes can still be feasible, we have a Highway Hierarchies-like demo available.

The glue between our Linked Data Fragments; the TREE specification can be used to create paginated, ordered, collections. But unlike similar vocabularies, TREE also describes what can be found by following a specific link. Supported descriptors include time ranges, geospatial regions, and textual patterns. For an example of the latter, have a look at the substring fragmenter that we created together with Netwerk Digitaal Erfgoed.

Comunica is already a great framework for querying the decentralized Web, and we added TREE support to make it even better. Development is still ongoing, but we have a pretty cool autocompletion demo up and running. All the resources this demo uses are hosted on Github Pages; it's like the classic jQuery autocompletion but better.

Do you have NGSI-LD data you want to make public, but the thought of having to manage a rate limiting and authentication service is holding you back? Consider publishing your data through a read-only view of cacheable data fragments. Clients can use these to answer any NGSI-LD query you may have; or you could even use SPARQL instead if you like semantics.

Education

Ghent University Ghent, Belgium

PhD in Computer Science Engineering March 2019 -

Linked Open Data publishing and Semantic Web technologies
International Semantic Web Research School Bertinoro, Italy

An annual summer school on Knowledge Graphs and Artificial Intelligence July 2019
Ghent University Ghent, Belgium

Master of Science in Mathematical Computer Science 2015-2017

Graduated with distinction

Master's dissertation: Data-flow analyses of dynamic programming languages
Ghent University Ghent, Belgium

Bachelor of Science in Computer Science 2012-2015