The Internet of Things is coming, but it needs a semantic backbone to flourish. With some 25 billion devices expected to be connected to the Internet by 2015 and 50 billion by 2020, providing interoperability among the things on the IoT “is one of the most fundamental requirements to support object addressing, tracking, and discovery as well as information representation, storage, and exchange.” So write the authors of Semantics for the Internet of Things: Early Progress and Back to the Future, Payam Barnaghi and Wei Wang, Centre for Communication Systems Research, University of Surrey, Guildford, UK and Cory Henson, Kno.e.sis – Ohio Center of Excellence in Knowledge-enabled Computing.
“The suite of technologies developed in the Semantic Web … such as ontologies, semantic annotation, Linked Data and semantic Web services … can be used as principal solutions for the purpose of realizing the IoT,” they state. “Defining an ontology and using semantic descriptions for data will make it interoperable for users and stakeholders that share and use the same ontology.”

Applying semantic technologies to IoT, however, has several research challenges, the authors note, pointing out that IoT and using semantics in IoT is still in its early days. Being in on the ground floor of this movement is undeniably exciting to the research community, including people such as Konstantinos Kotis, Senior Research Scientist at University of the Aegean, and IT Manager in the regional division of the Samos and Ikaria islands at North Aegean Regional Administration Authority.

Kotis, is among those embracing the opportunity, introducing the Semantic Smart Gateway Framework for supporting semantic interoperability between types of heterogeneous IoT entities, specifically with the proposal of an IoT ontology as the key technology for the abstraction and semantic registration of these entities, A paper, “Semantic Interoperability on the Internet of Things: The Semantic Smart Gateway Framework,” is to be published this year in the International Journal of Distributed Systems and Technologies.

The Semantic Web Blog recently had the opportunity to converse via email with Kotis on the topic:

Semantic Web Blog: Tell us a little bit about your background and how you have come to the Internet of Things as a focus of your semantic efforts.

Kotis: My research focus has been always on Knowledge Representation and Semantic Web technologies, with emphasis on the problem of semantic interoperability (ontology alignment methods and tools). Last year I [was] awarded a post-doc fellowship by the European Research Institute of Informatics and Mathematics (ERCIM) to research the topic of “semantic interoperability in Smart Environments/Internet of Things” at VTT Technical Research Centre of Finland. We (myself and the scientific coordinator of the program, Dr. Artem Katasonov) have worked towards a framework and a prototype system that demonstrated how it is possible to automatically interoperate heterogeneous IoT solutions and devices in IoT settings using an IoT ontology as a semantic registry — e.g. a house with semantically-described motion detectors and light switches that accepts commands from and sends status information to a semantically-described generic third-party application downloaded from an IoT app store!

Such a demo has been delivered as part of our contribution in the IoT project (TEKES-TiViT) in Finland. A short video of this demo is available here and a related poster is also available here.

Semantic Web Blog: Describe for us what an ontology of the Internet of Things is all about.

Kotis: An ontology for the Internet of Things provides all the necessary semantics for the specification of IoT devices as well as the specifications of the IoT solution (input, output, control logic) that is deployed using these devices. These semantics include terminology related to sensors and observations, reusing the one already provided by the SSN ontology (by W3C Semantic Sensor Network Incubator Group), and extended to capture also the semantics of devices beyond sensors — i.e. actuators, identity devices (tags), embedded devices, and of course the semantics of the devices and things that are observed by sensors, that change their status by actuators, that are attached to identity tags, etc.

Furthermore, and more importantly for our work, the ontology includes semantics for the description of the registered IoT solutions — i.e. input, output, control logic — in terms of aligning and matching their requirements with the specifications and services of the registered devices.

Semantic Web Blog: Explain to us how this can all play out in practical terms.

Kotis: In our work we have shown that an ontology can be used as a semantic registry for the facilitation of the automated deployment of generic and legacy IoT solutions in environments where heterogeneous devices also have been deployed. Such a service can be delivered by IoT solution providers, supporting remotely the interoperability problems of their clients/buyers when buying third-party devices or applications. Practically, this will require the existence of a central point — e.g. a web service/portal for both end users (buyers of the devices) and the IoT solution providers (sellers of the applications) to register their resources, i.e. both the devices and the IoT solutions, in an ontology-based registry.

Semantic Web Blog: What is the risk of moving into the Internet of things world without an ontology to ground it?

Kotis: The lack of explicit and formal representation of the IoT knowledge could cause ambiguity in terminology, hinder interoperability and mostly semantic interoperability of entities in the IoT world. Furthermore, lack of shared and agreed semantics for this domain (and for any domain) may easily result to semantic heterogeneity — i.e. to the need to align and merge a vast number of different modeling efforts to semantically describe IoT entities, efforts conducted by many different ontology engineers and IoT vendors (domain experts). Although there are tools nowadays to overcome such a problem, it is not a fully automated and precise process and it would be much easier to do so if there is at least a partial agreement between the related stakeholders — i.e. a commonly agreed IoT ontology.

Semantic Web Blog: How does your work relate to other ontology efforts?

Kotis: [So,], the IoT ontology (found here) that we have devised for the proposed Semantic Smart Gateway Framework (SSGF) and the Smart Proxy proof-of-concept implementation [as mentioned above] reuses the SSN ontology and the DUL (DOLCE Ultra Light) upper ontology. There are also other attempts to develop an IoT ontology, but these do not fully support the aim and goals of our work, and moreover they do not reuse existing vocabularies (such as SSN and DUL) or other ontology design patterns such as the one we use for representing ontology alignment information between ontologies. An extensive discussion on related work, and how our work is different from that, is provided in our journal paper (in press of International Journal of Distributed Systems and Technologies).

Semantic Web Blog: Can you tell us a little more about a couple of the high points we will see in your paper, Semantic Interoperability on the Internet of Things: The Semantic Smart Gateway Framework?

Kotis: Beyond the extensive discussion on related work, and how our work is different from that, in our journal paper (in press of International Journal of Distributed Systems and Technologies), you will be able to find a detailed scenario and motivation section, a detailed description of the main classes/properties of the ontology, and last but not least, a section where we demonstrate (in N3 notation) the use of the ontology in the prototype implementation of Smart Proxy for the semantic registration and matchmaking of IoT entities.

Another important point of our paper is the section presenting the ontology alignment tools that we have developed as part of the Smart Proxy system to support the semantic interoperability of devices’ and applications’ semantics. These tools have been evaluated and presented (in a poster) in the OAEI 2012 contest of Ontology Matching workshop in Boston, USA, in the context of the ISWC 2012 conference.