[Zope] REQUEST.zzz or REQUEST['zzz']

[Hans-Dieter Stich]

hi Zope gurus,

which of the following ways to access the attribute 'zzz' of a form request is 
the right one and why:

<dtml-var "REQUEST.zzz">

or

<dtml-var "REQUEST['zzz']">

TIA!

/hd