After much coding, experimenting, and discussions, we realised that some choices regarding the core frameworks. We began exploring Eclipse Kuapua and Kura to realise that they have a steep learning curves. Meanwhile, we played with Node-RED much successfully... while a third contender is OpenHAB.
Each of these frameworks has strengths and weaknesses but these are not obvious at first and choosing one over the others could ease some parts of the development while also closing some avenues in the future.
Consequently, we decided to explore a very simple running example of one sensor, one such framework, and one "output" running Kura to control an output screen. Below is a simple sketch of this running example, with the current hardware and IP addresses and ports:
