[Catalog-sig] Rating feature

[Terry Reedy]

Sridhar Ratnakumar wrote:

> 
> Yes. If PyPI is going to have release-specific ratings, I suggest that 
> each PyPI page (distname-version) show two rating bars:
> 
> a) release rating (logged-in user editable)
> b) overall rating (averaged from all release ratings)

I would make the second an average over all past releases
I would also suggest making it a so-called exponentially weighted 
average. Assume that past ratings are frozen and the individual votes 
tossed, the update when a new release arrives would be something like

past = .8 * past + .2 * current # adjust weights to taste
current = <undefined>

This way, a blunder release, once corrected, would have limited effect 
on the overall average and its effect would disappear with time.