opaque ids vs. natural keys

[Ian Booth]

> 
> My understanding of the sprint in Oakland is that we'd not tackle
> nesting at this point, which means in theory we'd just need a simple
> attribute saying "contained": "lxc" for the unit itself. This seems a
> few order of magnitudes simpler than changing primary keys like that,
> but I may be missing what this is all about.
>

Just as a heads up - we are not doing nesting now. We are ensuring the design
changes made now to support containers will also support nesting later on when
we do need to provide that feature.