CoAP/EXI, JSON protocol binding, XML schema and WSDL modifications

["Markus Jung" <mjung@auto.tuwien.ac.at>]

Dear TC members,

as new OASIS member I would like to say hello from the Vienna University of Technology to all oBIX members.

As research assistant at the automation systems group I am involved in several research projects (smart grids, Internet of Things) that include the integration of home and building automation systems.

Within the IoT research project we are working with the new IETF protocols for constrained RESTful environments (https://datatracker.ietf.org/wg/core/charter/), mainly CoAP which can be roughly seen as a UDP based HTTP equivalent, but with some additional features like asynchronous and group communication and due to the UDP binding also some features for confirmed messaging.

Within this project we aim using oBIX on constrained devices with a CoAP protocol binding. We have also developed a gateway that allows providing such an interface for existing home and building automation technologies like KNX, BACnet, ZigBee and Wireless Metering Bus. For the encoding we additionally provide an EXI (http://www.w3.org/XML/EXI/), EXI schema informed and JSON encoding.

Therefore, we would like to contribute to the oBIX standard these new protocol bindings. For CoAP as a HTTP equivalent it can be straight forward, although the CoAP observe feature allows to efficiently replacing the watch concept of oBIX.

If an XML schema of the oBIX object model is used the EXI encoding is as efficient as the oBIX binary encoding but relies on a standard W3C recommendation that is already implemented in several open source project and is not specific to oBIX. We didn't find a schema attached to the standard so we have defined it by our own. 

We also implemented the SOAP protocol binding and the schema is also useful in this case and allows to create platform specific types for the oBIX object model. But for a direct WSDL import to Java it was required to modify the provided WSDL slightly. We would also like to discuss these changes within the TC.

So to summarize our intentions we would like to contribute to oBIX:
-) new protocol bindings and encodings (CoAP, EXI, JSON) 
-) XML schema for oBIX object model
-) modifications to the SOAP WSDL

You can find details on our gateway, the protocol bindings and evaluation results within this paper: https://dl-web.dropbox.com/get/oasis-share/pitsac_2013_cameray_ready.pdf?w=AAAQ1enmFXofVf1RFmP8CXz6joHmifX-2NvbjfAj1j2LEQ

The reference implementation of protocol bindings and the gateway will soon be deployed as open source project.

I am looking forward to a fruitful discussion at the next telephone conference.

Best regards

Markus Jung
mjung@auto.tuwien.ac.at

Research Assistant
Institute of Computer Aided Automation
Vienna University of Technology
www.auto.tuwien.ac.at