Web Services for the Internet of Things through CoAP and EXI

According to the Internet of Things (IoT) vision, everyday objects such as domestic appliances, actuators and embedded systems of any kind in the near future will be connected with each other and with the Internet. These will form a distributed network with sensing capabilities that will allow unprecedented market opportunities, spurring new services, including energy monitoring and control of homes, buildings, industrial processes and so forth. In this paper, we concentrate on the actual implementation of the communication technology, adopting the Representational State Transfer (REST) approach. REST only relies on the HTTP methods such as GET and POST. Embedded communication devices are addressed using Universal Resource Indicators (URI) and data is exchanged through standard XML. We present our TinyOS design and implementation of two components that will play a fundamental role in the communication stack of REST-based devices. First, we focus on the Constrained Application Protocol (CoAP), which allows REST--based communications among applications residing in distributed and networked embedded systems. Second, we present our lightweight implementation of a EXI library: an efficient binary compressor for XML data files. Experimental results are provided in terms of compression, decoding (EXI) and access time (CoAP) performance.