EnvGuard : Guaranteeing Environment-Centric Properties in Web of Things

With the accelerated advancement of IoT, diverse devices are ubiquitously deployed in environments. Building on this, Web of Things (WoT) further integrates fragmented device services and provides unified interfaces using standardized Web technologies, promoting the development and deployment of WoT applications to sense and regulate the environment. However, disparate WoT applications independently control devices in the WoT environment, causing interference among devices and with the environment. This results in device behaviors that deviate from user expectations, causing violations of the user's desired environment properties. The intricate interplay of applications, user activities, and environment changes makes identifying and resolving potential violations a complex task. In this paper, we introduce EnvGuard, an environment-centric approach for property description, violation identification, and resolution in WoT environment. EnvGuard proposes a conceptual schema to model the relationship between device services and environment context, and automatically extends the conceptual schema into a specific environment representation based on device and space information. Furthermore, EnvGuard employs a template-based approach, enabling users to describe spatial and temporal properties based on the abstract device effects on the environment, and translating properties description into formal expressions. EnvGuard adopts a hybrid model checking method to respectively identify the spatial and temporal violations, and a resolution strategy that align with user intention is proposed to resolve violations. We evaluate EnvGuard through user studies and our proposed dataset, which is constructed by collecting real-world data from a laboratory WoT environment and manually labeling ten types of violations. The results confirm the usability, feasibility and efficiency of EnvGuard.