Multi-layered PKI implementation

["Grant Thomas" <eldowan.debian@gmail.com>]

Alright, I'm not sure that the subject line is completely correct, so
please bear with me.

When large buildings are keyed for locks, locks can be keyed for
different layers of security.

So, there might be the highest key, or skeleton key's used in old
houses that opened all the doors, and multiple levels of sub keys,
down to a key that opens only one lock.

I think I have a grasp on the basics of PKI as it relates to X.509
certificates, but I'm wondering if there is a PKI implementation that
allows for multiple layers of access built into the keys themselves.

I don't know if this is possible, or even desirable.

Thanks for any input or ideas,
Eldowan