HOBBIT Link Discovery Task at OAEI 2017.5

Task Motivation

The number of datasets published in the Web of Data as part of the Linked Data Cloud is constantly increasing. The Linked Data paradigm is based on the unconstrained publication of information by different publishers, and the interlinking of Web resources across knowledge bases. In most cases, the cross-dataset links are not explicit in the dataset and must be automatically determined using Instance Matching (IM) and Link Discovery tools amongst others. The large variety of techniques requires their comparative evaluation to determine which one is best suited for a given context. Performing such an assessment generally requires well-defined and widely accepted benchmarks to determine the weak and strong points of the proposed techniques and/or tools.

A number of real and synthetic benchmarks that address different data linking challenges have been proposed for evaluating the performance of such systems. So far, only a limited number of link discovery benchmarks target the problem of linking geo-spatial entities.

However, some of the largest knowledge bases on the Linked Open Data Web are geospatial knowledge bases (e.g., LinkedGeoData with more than 30 billion triples). Linking spatial resources requires techniques that differ from the classical mostly string-based approaches. In particular, considering the topology of the spatial resources and the topological relations between them is of central importance to systems driven by spatial data.

We believe that due to the large amount of available geospatial datasets employed in Linked Data and in several domains, it is critical that benchmarks for geospatial link discovery are developed.

The proposed Task entitled “HOBBIT Link Discovery Taskk” is a task of OAEI 2017.5.

Task Overview

The aim of the Task is to test the performance of Link Discovery tools that implement string-based as well as topological approaches for identifying matching spatial entities. The different frameworks will be evaluated for both accuracy (precision, recall and f-measure) and time performance.

Q & A

For more information send an e-mail to: Tzanina Saveta (jsaveta@ics.forth.gr) and Irini Fundulaki (fundul@ics.forth.gr).

Preliminary datasets are available.

March 1 (extended)
System registration using this form.

March 9 (extended)
Final datasets available in HOBBIT.

March 30 (extended)
Deadline for tool submission using HOBBIT instructions.

April 27 (extended)
Evaluation completed

Tasks and Training Data

We will use TomTom datasets in order to create the appropriate benchmarks. TomTom datasets contain representations of traces (GPS fixes). Each trace consists of a number of points.  Each point has time stamp, longitude, latitude and speed (value and metric). The points are sorted by timestamp of the corresponding GPS fix (ascending).

This version of the challenge will comprise the following tasks:

  • Task 1 (Linking) will measure how well the systems can match traces that have been altered using string-based approaches along with addition and deletion of intermediate points.As the TomTom dataset only contains coordinates and in order to apply string-based modifications based on LANCE[1] we have replaced a number of those with labels retrieved from Google Maps Api, Foursquare Api and Nominatim Openstreetmap Api. This task also contains changes on date format and changes on coordinate formats.
  • Task 2 (Spatial) measures how well the systems can identify DE-9IM (Dimensionally Extended nine-Intersection Model) topological relations. The supported spatial relations are the following: EqualsDisjoint, Touches, Contains/Within, Covers/CoveredBy, Intersects, Crosses, Overlaps  and the  traces are represented in Well-known text (WKT) format.For each relation, a different pair of source and target dataset will be given to the participants.

Read the detailed description of the tasks and training data .


[1]   Saveta, E. Daskalaki, G. Flouris, I. Fundulaki, and A. Ngonga-Ngomo. LANCE: Piercing to the Heart of Instance Matching Tools. In ISWC, 2015.

March 1 (extended)
Systems can register using this form.