I am currently thinking that core to XP is their cost model of different ways of coding. Two people are looking at some code, and they think - that's not "good" enough, so they refactor to make it "better".  To pull that off, the people on the team need to have some concept of what is "better". Without a coding cost model, they would simply DTSSTCPW and leave it at that.  Why don't they leave it at that, and what do they decide to change it to?  --AlistairCockburn

''When you say "cost model", are you referring to the cost of making a change, or just to the model that lets us say X is better than Y?  --rj''

"X is better than Y."  Thanks, Alistair

e.g.
    P a. P b. ->  P.c  where P.c = P a. P b.  (combine two calls into one)
but what about
    [exp] ifTrue: [exp2] ifFalse: [exp3]   ?
are there some conditions where you refactor to polymorph?
thanks.

CodeSmell''''''s tend to be high cost. Removing them is good.