Defining interactions of WoT servients with causality relations

The communication between different IoT systems presents a series of challenges in the processing and analysis of the heterogeneous information managed by said systems. The W3C Web of Things (WoT) standard offers a common model to define those devices following the guidelines established by the Thing Description. One of the caveats of the WoT is that the Thing Description does not define behaviour, so there is no way to know if an interaction is the consequence of another one. Each IoT device is represented using a Thing Description as an individual entity by design. In this paper, we propose a mechanism to improve interoperability between devices, laying the foundations on how to establish a relation linking them. This relation is formed by two different entities: the "causes" and the "effects". These two entities are at the same time interactions affordances provided by the Thing Description schema of each thing involved. Cause-effect relations help to define how devices work with each other following an event communication strategy.