M4M or Measure 4 Measure, ever since Shakespeare's play with the same name we know, people can be mistaken for one another. A Duke (like the beloved Java mascot) claims to be a monk, the head of a dead pirate is presented to be that of the young hero. So can important information like Units of Measurement be misinterpreted. While humans reading 10°C, 10 C or 10 Degree Celsius, each of those could be interpreted and understood well enough. For M2M communication, unless a program is provided with a large glossary of alternate terms, only ONE of these would be acceptable.
Slides of the JCP EC F2F in January 2014 proposing the idea of a Units of Measurement JSR, recently approved as JSR 363: https://jcp.org/en/jsr/detail?id=363