OOP in Scheme

When should I use message passing or data-directed programming? What are the advantages/disadvantages of these techniques over the OOP we can find in Java for example.

>>2
The way I saw it, ``message directing" is OOP.

The objects are more than just tagged data as in data-directed programming; they also contain their behavior.

>>4
I'll check CLOS out eventually, but I like the ``minimalism" of scheme.