Hypermedia APIs for Sensor Data: A pragmatic approach to the Web of Things

As our world becomes more instrumented, sensors are appearing in our homes, cars, and on our bodies. These sensors are connected to a diverse set of systems and protocols driven by cost, power, bandwidth, and more. Despite this heterogeneous infrastructure, we need to be able to build applications that use that data, and the most value comes from integrating these disparate sources together. Infrastructure for the Internet of Things (including not just consumer products but sensors and actuators of all kinds) is becoming more commonplace, but we need an application layer to enable interoperability and create a Web of Things. Here we introduce a pragmatic, hypermedia approach to the Web of Things, integrating HTTP request/response interactions with realtime streaming using HTML5 WebSockets. We will discuss how our approach enables client/server interactions that are both evolvable by the server and discoverable by the client. Rather than attempt to define yet another competing standard, we incorporate a collection of complementary standards already in use. We will also describe our implementation of these concepts in ChainAPI, a sensor data server in use by a variety of projects within our research group. We will describe one of several end-to-end applications as a successful case study.