[Tagging] How do you say "no" with semicolon'ed lists? Re: Facts and opinions

[Rory McCann]

On 08/01/2019 08:30, Simon Poole wrote:
> and yes you could even document that something is -not- sold in a
> structured fashion.

How do you do that? To me "sells:blah=no" is clear: that blahs are, by 
default, sold in this type of thing, but aren't here. Is there a 
standard way to do that with semicolon'ed values?