[plt-scheme] Relation to r6rs?

I've been reading the PLT Scheme guide and r6rs more or less in parallel 
and at times I've been scratching my head. Specifically, I don't 
understand how libraries (r6rs), modules (plt) and units (plt) are 
related.

Is there some general advice for writing/structuring code so that it is 
standard-conformant and portable and at the same time makes good use of 
what PLT Scheme provides on top or r6rs?

Michael

-- 
Michael Schuerig
mailto:michael at schuerig.de
http://www.schuerig.de/michael/