A new standards track RFC (RFC 8428) was published in August 2018. The RFC, which specifies Sensor Measurement Lists (SenML), is currently a Proposed Standard. Take a look at the document’s history at https://datatracker.ietf.org/doc/rfc8428/.
SenML is a notation for sensor measurements (values) and associated metadata. The metadata may include the id of the sensor, a unit, a timestamp, or the sensor’s location. Shortcuts for reporting multiple measurements from a single sensor, or measurements from multiple related sensors are defined. A number of representations for the measurements and metadata are allowed, including familiar JSON and less known CBOR (Concise Binary Object Representation). SenML-formatted data may be transferred with an application-layer protocol like CoAP or HTTP. A paper presented at the IAB-organized IoT Semantic Interoperability Workshop (held in 2016) described SenML as a “simple building block for IoT semantic interoperability.”
You can learn about SenML, if you take our course OBIR.