Many standards, projects, and platforms are being developed as the Internet of Things (IoT) is adopted in a wide range of fields. However, because each IoT platform is based on a different resource identifier (ID), it is difficult to identify each device and use the service among heterogeneous IoT platforms. To solve this problem, we propose an interoperability framework that includes an IoT resource name system (RNS) based on analysis of the resource IDs (i.e., device ID and resource request formats) of five selected IoT platforms: oneM2M, Oliot, Watson IoT, IoTivity, and FIWARE. The IoT RNS converts a specific resource path into a resource request format for each platform. The converted resource path is shared among IoT RNSs for each platform, and users can request services from other platforms using converted resource paths. We also present an example of interoperability scenario among heterogeneous IoT platforms using the proposed IoT RNS in a smart city. The scenario includes each stage, such as resource registration and deletion, sharing mapping tables, converting resource addresses, and service requests. Furthermore, to prove the aims of the proposed approach, we implemented the resource interoperability scenario between oneM2M and FIWARE. In the experiments, resources can interwork in the two platforms through resource path conversion. Based on the results, we performed a qualitative evaluation of the IoT RNS with the current studies. In conclusion, our proposal overcomes the issues of building an existing integrated platform or specific central ontology and duplicating resources inside the platform. In addition, we separate the functions of the root and local IoT RNSs to solve communication traffic and memory capability issues.
Internet of Things (IoT) technology is developing and expanding in various fields such as smart homes, healthcare, smart cities, logistics, and smart car. The international standard, “ISO/IEC 20924:2018 Information technology—Internet of Things (IoT)—Vocabulary” (ISO/IEC, 2021), defines the IoT as the “infrastructure of interconnected entities, people systems, and information resources together with services that process and react to information from the physical and virtual world.” In other words, the IoT is hyper-connectivity among smart things, services, and humans to provide useful and seamless services regardless of the types of networks, devices, and platforms and with minimum human involvement. These technologies, related standards, projects, and platforms are continuously being developed (Lee et al., 2021). In particular, IoT platforms are an essential factor in providing interoperability because they support the network connection to various devices (e.g., sensors and access points) and provide services to users. According to the IoT Platform Companies Landscape & Database 2020, the official number of IoT platform companies in the open market is more than 620, up from 450 in 2017. For example, many platforms (e.g., AllSeen Alliance AllJoyn, Apple HomeKit, oneM2M, FIWARE, Google Cloud IoT, GS1 Oliot, IBM Watson IoT, Microsoft Azure, and OCF IoTivity) are being developed to provide various services. Therefore, interoperability, such as requesting services and sharing resources among diverse IoT platforms, is important, and it is an essential factor for building a real IoT environment that provides seamless services regardless of the type of IoT platform.
IoT technology is rapidly expanding in many fields, including smart homes, logistics, automobiles, healthcare, and smart cities, and related standards, projects, and IoT platforms are constantly being developed and improved. However, the numerous platforms and related standards make it difficult to achieve interoperability and collaboration among platforms. In particular, identifying each resource among heterogeneous IoT platforms is challenging due to various ID formats.
In order to solve this problem, we firstly classified interoperability taxonomy in IoT environments into middleware, network, syntactic, and semantic interoperability, with common security factors for each case. In addition, we proposed an IoT RNS architecture and scenario in a smart city to convert IDs between heterogeneous IoT platforms. Finally, we compared the proposed IoT RNS with existing projects under development and showed it satisfies the interoperability in the heterogeneous IoT platforms.
Future studies will expand interoperability by considering security and implementation-related issues in a real environment. Device authentication and authorization will be added to resource sharing among heterogeneous platforms to address particular security issues. Defining these security policies and applying them to IoT RNS will allow restrictions to be applied for unauthorized access to heterogeneous platform resources.