perkeep/doc/arch.md

# Architecture

First, read [the terminology](terms.md).  Given that, this picture better explains
the overall picture:

<img src="https://docs.google.com/drawings/pub?id=1-0QYgyOnjL7hvdEbq77BzkewPJ6BY-bLYCtYFFii77A&amp;w=768&amp;h=576" width='768' height='576' />