[plt-scheme] show me your behaviour

hi,

I have what is by now an old question i'm sure, but i'm not sure where
to find previous discussion. From "The Structure and Interpretation of
the Computer Science Curriculum"
http://www.ccs.neu.edu/scheme/pubs/jfp2004-fffk.pdf

'Show me your [code] and conceal your [data structures], and I shall
continue to be mystified. Show me your [data structures], and I won’t
usually need your [code]; it’ll be obvious.'

How to people re-consider this in light of
interface/behaviour/role/collaboration i.e. the OO approach to
analysis, modeling, design, and implementation?

thanks.