XML-less EXI with code generation for integration of embedded devices in web based systems

Abstract

XML is a widely used as message serialization format in web-based open and heterogeneous systems because of its flexible data model. Internet-of-Things (IoT), or network with constrained nodes, is expected to be heterogeneous, and flexibility and expressiveness of XML are also good for IoT. However, RAM and bandwidth constraints on such nodes make handling of XML difficult. The authors are developing XML-less EXI to solve the problem. Our approach adopts Efficient XML Interchange (EXI) as alternative serialization form of XML. It solves the bandwidth problem of XML. At the same time, the authors apply code generation techniques to encode/decode EXI stream without XML data models on constrained nodes. Static state machines from a schema-informed EXI grammar enable constrained nodes to convert EXI data directly from/to its internal data. The authors show that XML-less EXI is highly efficient in RAM usage regardless of the size of an EXI stream and more compact in ROM size than other implementations. The authors also provide code size estimations for a set of schema-informed EXI grammars and insights on how to make the grammars compact.