2015-10-20 UTC
# 
csarven elf-pavlik Nothing prevents you from using any arbitrary string in class/rel (for obvious intents and purposes). Just don't expect that anyone else will be able to consume and use it appropriately or *understand* what it means. If you want "headsign" or something alike to have wider adoption, you have to go through the mf process and document which markup patterns are currently used on the Web. You then derive a term which resembles that. In a nutshell.