Making Smart Buildings and Personal Systems Cooperate via Knowledge Base Overlays.

Reactive IoT applications often have to deal with the data source Babel arising from their need to operate on context information originated from different data sources. Semantic knowledge bases can be fruitfully deployed to alleviate this problem: they provide a unified access point for context information including both long term (such as the structure of the environment) and transient (such as sensor readings) data thanks to their ability to host elements responding to different schemas within the same container. In previous works we introduced an architecture to create reactive IoT systems based on a semantic knowledge base that also hosts the definition of their behavior and on an accompanying reactive machinery. In this paper, we introduce the use of knowledge base overlays, i.e. containers providing a live, unified view over (parts of) different underlying knowledge bases, as a mechanism to enable interoperation between multiple IoT semantics-based systems. Specifically we explore the benefits of this approach in a case study in which a semantic IoT system governing a smart building interacts with the personal semantic systems of the people entering the building.