Hi Christoph,
Thanks for pointing that out. No, I had not found that page. Search terms including colons are difficult! After your clue, I know that the better search team would have been “Units of Measurement”. With that I was also able to find the corresponding article in the OpenHAB documentation.
I think there’s a good case for some mention of this feature being added to the rules article.
So, the final outstanding question is how to create variables with UOM in the rules DSL. I tried myVariable [℃], but that could not be parsed. I would rather avoid the nasty practice of “magic numbers”, especially when they’re being using in multiple places in the same file.