re understanding cfengine "passes"

[rader]

The doc says that cfengine is a one pass interpretator.  But I 
suspect that's not quite correct... to wit...

The cfagent --verbose output from my config says that cfengine is
doing two passes. 

Using...
  addInstallable = ( has_afs )
  import: afs.conf  # defines has_afs
  shellcommands:
    has_afs:: "/bin/echo yes i have afs here"
    !has_afs:: "/bin/echo no afs here" 
...causes *both* shellcommands actions to be excuted (in other words:
causes another pass of doing shellcommands.)  The cfagent --verbose
output says shellcommands is executed twice during the first pass.

Would some kind person please clarify?  It seems like cfengine must
have two "dirty" flags: a "global dirty flag" that says "need to do
another pass" and a "define dirty flags" that say "need to redo
this pass because something on my addInstallable list was defined."
Assuming that's correct, under what circumstances does the global
dirty flag get set?

TIA.

steve 
- - - 
systems & network guy
high energy physics
university of wisconsin