[gclist] Name that hypothesis

[Nick Barnes]

> What is the name of the following hypothesis?
> 
> 	"Most references in a system point backwards in time, i.e. from
> 	 younger objects to older objects."
> 
> In the GC community we all know this, and many of us use it
> frequently, but we don't seem to have agreed on a name for it.

By the way, I suggest "The directional hypothesis", with the weak
variant being as above and the strong variant replacing "most" by
"all" (and being true of some implementations of some strong
functional languages).

Nick B