About computer-optimized RDF format.

I was wondering how to improve the loading time of RDF files in
semantic web frameworks.
And then came a question: is RDF efficient to load?
The obvious answer is no.
Making it readable for humans makes it definitely slower to load in programs.
So I came to another question:
Is there a computer-optimized format for RDF?
Something that would make it load much faster.
For example by replacing URIs' string by integers, plus a lookup table
for correspondance.

A nice side effect would be that big RDF would be more compact to publish

Are there any studies about improving the format from a
parsing/loading/zipping perspective?