A Formal Methodology for Easing Development and Maintenance of Entity Services in Service Oriented Software-Defined Internet of Things

Internet of Things (IoT) systems are usually built with entity services, which are those abstracting functionalities of sensing and executing devices in the physical space. As requirements of sensing or controlling the physical space can be varied with different systems, entity services are supposed to be easily adapted to meet such dynamicity. To ease updating and modification of entity services, although a software-defined network approach has been applied in building IoT systems, entity services developed with the same software architecture as traditional services on the Internet have an inherited problem in adaptability. In order to solve the problem, we abstract the functionalities of an entity service in social, cyber, and physical spaces into application model, sense-execute model, and physical model, respectively, and propose a physical model driven software architecture (PMDA) for guiding design of entity services. To ease development of entity services, we also propose a formal development method of entity services (fDES) to transform the abstracted models of PMDA into implementable software modules. Besides, to reduce maintenance cost of entity services when adapting them to different requirements from the social space, we propose a formal maintenance method of entity service (fMES). The correctness of fDES and fMES is verified by a case study, and their effectiveness in reducing cost of developing and maintaining IoT systems composed of large-scale frequently changed entity services is proved by analysis.