Towards the linking of geospatial government data

A study on the semantic harmonisation between data from Dutch geo-registries

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The growing complexity of many projects and applications require methods that help integrate vasts amounts of data coming from different sources. In all cases, semantic interoperability plays an important role - the meaning of content should be organized logically, as to allow machines to interpret it. The Semantic Web vision has been developing standards to support this idea, with the goal of creating a 'web of data', were pieces information can be accessed and linked to one another consistently. The ideas behind Linked Data have been explored in different areas of study. The geospatial domain presents an interesting challenge, as geospatial data offers many different views on the same physical universe. This is especially the case with geo-registries - collections of official geospatial data used by governments. This data already contains links in the form of spatial relations. However, there is no consensus on how these links should take form. Thus, this research will explore how linkable geospatial data from registries actually is by answering the following question:"To what extent can ontology-based solutions using semantic web technologies contribute to the integration and use of data from geo-spatial registries?". This question is broken down in three sub-questions that address ontology-based integration techniques (including tools and languages), the impact of dataset characteristics and the added value of semantic relations. The research includes a literature study to provide a theoretical background, a case study of two Dutch geo-registries (Basisregistratie Grootschalige Topografie and Basisregistrie Topografie) and a conceptual framework that is applied to the case study as a way to explore the main question. The results of this framework reinforce the importance of using instance-level data to understand the connections between different conceptual models and show the unavoidable subjectivity that is involved in the process - from the conceptualization of the data (model) to the creation of query rules. The findings indicate that the capabilities of ontology languages (such as OWL) are not necessarily practical for data from registries, and that custom processes might be necessary depending on the application envisioned by data users. Country-wide registries managed by different data owners and different interpretations of data acquisition rules will lead to inevitable variations in the registration of objects in datasets. And more efforts could be invested in providing quality indicators for alignments.