Abstract
This paper presents a dynamic geospatial knowledge graph as part of The World Avatar project, with an underlying ontology based on CityGML 2.0 for three-dimensional geometrical city objects. We comprehensively evaluated, repaired and refined an existing CityGML ontology to produce an improved version that could pass the necessary tests and complete unit test development. A corresponding data transformation tool, originally designed to work alongside CityGML, was extended. This allowed for the transformation of original data into a form of semantic triples. We compared various scalable technologies for this semantic data storage and chose Blazegraph™ as it provided the required geospatial search functionality. We also evaluated scalable hardware data solutions and file systems using the publicly available CityGML 2.0 data of Charlottenburg in Berlin, Germany as a working example. The structural isomorphism of the CityGML schemas and the OntoCityGML Tbox allowed the data to be transformed without loss of information. Efficient geospatial search algorithms allowed us to retrieve building data from any point in a city using coordinates. The use of named graphs and namespaces for data partitioning ensured the system performance stayed well below its capacity limits. This was achieved by evaluating scalable and dedicated data storage hardware capable of hosting expansible file systems, which strengthened the architectural foundations of the target system.
Highlights
General context of the paper — problem space Development of sustainable digitisation practices is widely recognised as an important part of roadmaps at organisational, industry [1], national [2] as well as international levels [3]
The system architecture for the Semantic 3D City Database proposed in this paper aims at closing some of the gaps, related to current built environment representation within J-Park Simulator (JPS) and The World Avatar (TWA)
To keep the architecture open to further collaborations and maximise the potential of its reuse and innovative modifications in the future, during the proof of concept stage of the database, research presented here was focused on open source stores
Summary
General context of the paper — problem space Development of sustainable digitisation practices is widely recognised as an important part of roadmaps at organisational, industry [1], national [2] as well as international levels [3]. Radermacher [4] points to the fact that global governing bodies, such as the UN, G20 and the World Bank, all agree on the importance of adopting digitisation standards for achieving international comparability. The World Avatar (TWA) is an all-encompassing dynamic knowledge graph. It is built on agent-based system [2,6] architectural principles as well as semantic web standards and recommendations provided by the W3C. Answering to inter-domain interoperability problems is at its core
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