What makes a cabin a certain class?

Hi
I'm curious - obviously there are certain classes available on airlines - e.g. economy, premium economy, business, first, etc.
A bit of a geeky question, but what determines whether a cabin/the services offered in that cabin meets that class?
I.e. are there certain criteria that have to be met? Do they have to charge certain amounts for the tickets?
E.g., could VS, if they so wished, decide that UC was now 'First Class' and ticket it as such (apart from the fact that it might not compare to FC products with other airlines)?
Hope I've explained that OK!
Thanks
Andy:)
I'm curious - obviously there are certain classes available on airlines - e.g. economy, premium economy, business, first, etc.
A bit of a geeky question, but what determines whether a cabin/the services offered in that cabin meets that class?
I.e. are there certain criteria that have to be met? Do they have to charge certain amounts for the tickets?
E.g., could VS, if they so wished, decide that UC was now 'First Class' and ticket it as such (apart from the fact that it might not compare to FC products with other airlines)?
Hope I've explained that OK!
Thanks
Andy:)