## 7 Conclusions  
A central objective of this paper has been to discuss how Semantic Sensor Web approaches can assist in the process of integrating smart devices into future Internet-of-Things infrastructures populated by Web-accessible, heterogeneous and geographically dispersed sensor networks. We have argued that besides enjoying the benefits offered by the growing availability of Web-accessible sensor data, smart devices can also play an important role in _generating_ valuable real-world information to be shared across the Semantic Sensor Web. We have taken the OGC SWE initiative as a reference of service structure to integrate smart devices into the Sensor Web, and presented a _Ubiquitous Sensor Network (USN) Platform_ as a suitable framework to both integrate smart devices over Next-Generation Networks and provide efficient mechanisms to discover, access and publish real-world information. We have then explored experimentally how the USN-Platform may be extended to support Semantic Web technologies, which will allow smart devices to be more efficiently integrated with the future Semantic Sensor Web. As a main conclusion, based on our ongoing functional and experimental activities we believe that the use of Semantic Web principles and technologies can help overcome major obstacles to integrate smart devices and real-world data. However, the scalability and efficiency of intensive distributed computing will become critical factors as the amount of data increases with the development of large-scale scenarios with connected objects (as intended for the Internet-of-Things). We will address these factors in further research. The scalability of our Telco Platform is determined by two main features: component distribution and the current state of the art offered by big-data solutions (such as MongoDB ([[http://www.mongodb.org/](http://www.mongodb.org/)]([http://www.mongodb.org/](http://www.mongodb.org/))) and Cassandra ([[http://cassandra.apache.org/](http://cassandra.apache.org/)]([http://cassandra.apache.org/](http://cassandra.apache.org/)))). These have proved to be enough for recent large-scale projects like SmartSantander. Nevertheless, the impact that the new semantic features will have on the scalability of the Platform has yet to be fully evaluated. This is the focus of part of our ongoing research efforts. To handle the increasing number of smart devices the Telco Platform relies on NGN scalability: it requires that the devices be registered (through USN-Gateways) as user terminals. However, the impact of the specific traffic patterns generated by future IoT environments is still an open area of research. Furthermore, for highly dynamic scenarios (such as those involving \"connected\" cars), with the added time constraints imposed by taking into account also the interaction between the human user and the smart system, it will be necessary to develop mechanisms for information fusion, transport optimization and node mobility that can guarantee short reaction times. The Semantic Sensor Web initiative (SSW) [44] proposes the use of ontologies and other Semantic Web technologies to enrich data from heterogeneous sensor networks. The main purpose of the SSW is to provide a unified formal representation of sensor (and sensed) data, adding semantic annotation to existing standard Sensor Web languages. There are many proposals to semantically annotate sensor observations. Among them, as reviewed by the W3C incubator group on SSN [13], XLink, which is already used in SWE documents, or RDFa, which defines attributes that can be added to SensorML and O&M documents (as we did in our previous work [45]). Acknowledging difficulties identified by the W3C SSN Incubator Group, particularly the multiple interpretations of XLink within the OGC community and the lack of a systematic way to port RDFa specifications to an XLink base, in the present paper we have followed the semantic representation of O&M that was proposed for the Semantic Sensor Observation Service (SemSOS) of [PERSON] and colleagues [14].