Exploiting House Log of Home Network System to Derive Contexts with Past Situations

In the conventional context-aware services of the home network system (HNS), every context has been defined by current (or recent) situations only. Considering past situations in a house would significantly extend the expressive power of the context-aware services. In this paper, we propose a new type of context, called log context, by using house log of the HNS, extensively. The log context is defined with both the current and past situations, where the current situation is obtained by sensors or device status of the HNS while the past situations are derived by queries to the house log. We also develop a system that can derive the log contexts within an actual HNS. To manage individual log contexts efficiently, the system is designed by four layers: application layer, log context layer, log query layer, and DB connector layer. Using the developed system, we evaluate practical log contexts: "It is much colder than yesterday", and "Today is the coldest day for past several years".