As far as I know there are litttle to no standards at all to represent information specifically related to smart meter messages. Nevertheless, "traditional" information representation languages and meta-languages can be used, that is to say, JSON, XML, etc. In this paper (http://www.mdpi.com/1996-1073/7/9/5953) an example on how to use semantically enriched messages is used exploying SPARQL requests from the application layer and XML messages for data registration, requests and answers from the hardware devices.