WoT2Pod: An Architecture enabling an Edge-to-Cloud Continuum

We present WoT2Pod, an architecture that provides a uniform API for data access and control of IoT devices at the edge and in the cloud, creating a seamless continuum between these environments. The uniform API is based on Resource Description Framework (RDF) graphs, Linked Data Platform (LDP) containers, and HTTP. The API is created by a middleware that uses the Web of Things to interact with devices, maps collected IoT data to RDF, provides the most recent data at the edge, and stores data for long-term storage and sharing with third parties in a Solid Pod in the cloud layer. We establish a formalism and derive equations for predicting latency, and use them to evaluate different polling and pushing-based methods for exchanging data between components. Our results underscore that interactions at the edge are consistently faster than those in the cloud, with data access 65% faster and device control 70% faster. We found that a strategy that relies entirely on pushing data provides the most optimal latency results.