SSIKG: A framework for spatial-semantic integrated indoor knowledge graph construction.

The demand for place retrieval and route guidance services of indoor environments has increased owing to the extensive development of large complexes. In comparison to increasingly customizable and diversified general place retrieval services, indoor place-related services currently offer few features. Existing knowledge graphs mostly deal with limited spatial context based on geographic location, and hence do not cover indoor environments. In this study, we propose a framework for a Spatial-Semantic integrated Indoor Knowledge Graph (SSIKG) as a multi-layered model of the indoor environment. The spatial layer involves knowledge of navigable paths by preserving network-based topological relationships between places. Concurrently, the semantic layer expresses features from an end-user perspective. To assess framework utility, place retrieval tests with resulting graphs were performed for six practical use cases, returning lists of the places and their corresponding optimal paths. Finally, the results were reviewed in terms of spatial inference and expansion of our graphs.