## 1 Introduction
* USN Middleware, including functionalities for sensor network management and connectivity, event processing, sensor data mining, _etc_. * Network infrastructure, mainly based on Next Generation Networks (NGN). * Sensor networks. It is also important to underline that a USN is not a physical network, it is a conceptual architecture that makes use of existing networks. As Figure 1 illustrates, the USN has at its core a Next Generation Network (NGN) infrastructure, which provides ubiquitous connectivity and all the control and management network capabilities. This is the communications infrastructure, on top of which the Sensor Web layer can be fully integrated as a part of the USN Middleware. Based on this idea, the USN-based platform (USN-Platform) we propose integrates OGC SWE functionalities into the USN middleware through what we refer to as a USN-Enabler (see Figure 1). Furthermore, with the USN-Platform built around NGNs, the gap between the Sensor Layer and the Sensor Web Layer is bridged by means of USN-Gateways. As shown in Figure 1, it is through USN-Gateways that heterogeneous and geographically dispersed sensor networks and smart devices can be interconnected, discovered, accessed and controlled, using protocols and information models standardized by OGC SWE. Figure 1: Conceptual architecture of a Ubiquitous Sensor Network Platform to connect applications (e.g., smart devices) with sensor and actuator networks. (Components of the proposed semantic extension are also shown). Once the USN-Platform is in place to bridge the underlying heterogeneity of communication technologies, the opportunity arises for smart applications to combine and reason with different kinds of information from diverse sources. This is the second challenge we identified in the beginning. Semantic Web [12] technologies, an evolving extension of the current Web, are intended to provide well-defined and machine accessible information that is shareable across applications. Combining the Sensor Web and the Semantic Web we arrive at the notion of the Semantic Sensor Web (SSW). These technologies are being developed to provide formal descriptions of the entities related to sensor data, in particular the observations of real world features and the sensors that can capture them. For this purpose the W3C has produced a Semantic Sensor Network Ontology (SSNO) [13], which is a broad and complex conceptual structure. While acknowledging the central role that the Semantic Sensor Web is set to play in the future IoT, in this paper we present work that explores a first step of drawing the USN-Platform toward SSW technologies. It is, to our knowledge, the first time semantic technologies are included in a Telco IoT Platform. Nevertheless, we acknowledge that the Platform extension we have considered only handles semantic descriptions of observations (_i.e._, the data given by sensors) as a relatively simple set of concepts and relations following the SemSOS approach [14]. We will refer to the encoding of sensor observations in terms of said concepts and relations as _semantic annotation_. To accommodate this semantic representation of observations, the USN-Platform was extended with two elements (see Figure 1): one to enable the communications layer (USN-Gateway) to handle the semantically annotated sensor observations, and another in the service layer (USN-Enabler) to store these observations and allow applications to reason with the accumulated data. With this semantic extension the applications may themselves publish processed information that results from reasoning with sensor data and also with observations provided by human users through appropriate interfaces. With a \"semantically enhanced\" USN-Platform we aim to tap into the great potential that the exchange of semantic information can offer for the development of future applications for the increasing number of smart devices in circulation (mobile phones, connected vehicles, home appliances, _etc._).