The joint OGC and W3C standard SOSA/SSN ontology describes sensors, observations, sampling, and actuation. The W3C Thing Description ontology under development in the W3C WoT working group describes things and their interaction patterns. In this paper we are interested in combining these two ontologies for modeling Smart-Sensors. Along with basic sensors, a Smart-Sensor contains a micro-controller that can run different algorithms adapted to the context and a communicating system that exposes the Smart-Sensor on some network. For example, a smart accelerometer can be used to measure cycling cadence, step numbers or a variety of other things. The SOSA/SSN ontology is only able to model partially the adaptation capabilities of Smart-Sensors to different contexts. Thus, we design an SOSA/SSN extension, called the Semantic Smart Sensor Network (S3N) ontology. S3N answers several competency questions such as how to adapt the Smart-Sensor to the current context of use, that is to say selecting the algorithms to provide the right sensors outputs and the micro-controller capabilities.