Wher is the ProgramGeneratorImpl class ?

[Pierre-Yves Saumont]

Hello,

I am trying to use Cocoon. I compiled it and tried the samples. Now, I 
am trying to make my own app working. I get the following exception :

java.lang.ClassNotFoundException: 
org.apache.cocoon.components.language.generator.ProgramGeneratorImpl


I thinks I am missing some jar, but I could not find the missing class 
in any Cocoon jars or dependencies. Can somebody tell me where it is 
supposed to be ?