Visitor Design Pattern and DP Componentization - 
a good article & links: 

Meyer & Arnout: Componentization: The Visitor Example, CACM 6/2006 (23-30)

Bertrand Meyer and K Arnout wrote this survey 
using Visitor DP as an example. They conjecture a
large fraction of GOF DP's could be componentized,
giving specifics.

Bob Lechner
RJLRef: $PH/06f522/VisitorDP060722.txt