While working on #226, it was a bit challenging to implement the various algorithms just by reading the prose.

For example, in https://w3c.github.io/ppa/#clear-site-data, the phrase "all epochs" is a bit ambiguous: I believe it means all epochs between the minimum epoch and the current one for the affected site, but it could be interpreted as "all epochs for which the affected site has an entry in the privacy budget store", as the obvious implementation for literally all epochs (add synthetic zero-valued entries for every epoch from the minimum up to the current one) is potentially expensive. I think it would help to have an explicit algorithm for this for clarity.

https://w3c.github.io/ppa/#clear-browsing-history would likewise benefit from a series of steps.