I. Introduction
In the end of the eighties, a visionary sentence by Mark Weiser [1] put the basis for the current Internet of Things (IoT), definition appeared for the first time only ten years later [2]. Weiser stated that ”the most profound technologies are those that disappear” [1] and this is very close to what the IoT is building around us. Many are the application domains where the IoT is employed and several are the steps that brought to the Internet of Things (i.e., pervasive or ubiquitous computing [3], context-aware computing [4]), but one thing remained unchanged: the central role of the context. Abowd et al. provided a definition of context that is the one most commonly accepted in literature: ”context is any information that can be used to characterize the situation of an entity. An entity is a person, place, or object that is considered relevant to the interaction between a user and an application, including the user and applications themselves” [4]. The Internet of Things is gradually evolving towards a new direction known as Semantic Web of Things [5], where the main focus is on the adoption of technologies belonging to the area of Semantic Web [6]. The Semantic Web was born to transform the Web from a repository of human-readable information into an entity that allows for the machine-understandability of data. This vision is becoming reality thanks to a layered structure known as Semantic Web stack. The main components of this stack allow: 1) the univocal identification of resources thanks to IRI (International Resource Identifiers); 2) t he representation of data as a set of triples thanks to RDF (Resource Description Framework) [7]; 3) the definition of a vocabulary to clearly state the meaning of represented data by the means of RDFS (RDF Schema) [8] and OWL (Web Ontology Language) [9]; 4) the storage and retrieval of data via the SPARQL Update [10] and Query languages [11].