A Semantic IoT System for Indoor Environment Control based on Sensor and Actuator Support Toolbox

Abstract

The vision of the Internet of Things (IoT) is to connect devices all over the Internet to share and exchange data in order to provide useful services to people. According to Cisco's predictions there will be more than 50 billion devices connected to the Internet by 2020. These devices will generate huge amount of data to be acquired by many services and application in areas such as smart homes, smart grids, healthcare, and environmental monitoring. These devices are of heterogeneous nature, producing data in various different formats and requiring different protocols to communicate. This makes interoperability one of the most fundamental requirements to support various tasks such as object addressing, tracking and discovery as well as information representation, storage and exchange. Recently, different semantic technologies such as ontologies, semantic annotations, linked data and semantic web services have gained popularity specifically in the connected devices domain. In this thesis we have used semantic technologies to overcome the issue of interoperability in an indoor IoT system for environment control. The proposed system is an indoor environment monitoring and controlling application that collects data from different service domains/ service modules it is built upon. To provide interoperability between these domains in order to use their services, we are using semantic technologies. Each service module collects data from its respective domain, and stores and handles the domain knowledge using ontologies. Semantic sensor service provider module is used to collect real time sensing data and sensor information, semantic actuator service provider module is used to exchange messages between the actuators and the top modules, and GIS service provider module provides the location information of these devices. The functionality of these modules is to process this data and provide it to the top module which is the application server. The main idea is to provide an integrated application server that handles the knowledge retrieved from the service modules using semantic technologies. Application server integrates device information with its respective location information and stores it in RDF form in the application server ontology. This enables semantic interoperability between all the service modules in the system based on the integrated knowledge. We have developed a toolbox for each module that handles the data creation and storage in the ontology. The data stored by each service module in its ontology can be manipulated using the toolbox associated with it. Each ontology model is a formal representation of the knowledge or context within a service domain. This facilitates effective data access, integration, resource discovery, semantic reasoning and knowledge extraction. Semantic description can be applied to various resources in IoT. An ontology for the Internet of Things provides all necessary semantics for the specification of IoT devices as well as the specifications of the IoT solution that is deployed using these devices. These semantics include terminology related to sensors and observations that is already defined by the SSN ontology. In this thesis we reused the SSN ontology for basic definition of sensors and its observations. System evaluation is performed by comparing the system performance with SQL technology and with hybrid approach including both SQL and SPARQL technologies.