[Zope] Question about __ac_permissions__ and more generally about the do cumentation

[Bocquillon Philippe]

Hello

In the following piece of Python code for Zope:

__ac_permissions__=(
	('View management screens', ('manage_main',)),
	('View', ('', 'index_html', 'update',
		  'show_source','view_image','picture',)),
	('Change', ('manage_edit',), ('Manager',)),
	)

Could you tell me:

1) What does the first "empty" method ('') associated to the View permission
mean?
2) Is the Manager method associated with the Change permission the class
constructor for a Manager class which would represent the Manager role?
3) Why is Manager method needed in addition to the manage_edit one? 
4) Why are there 2 tuples associated with the Change permission instead of
having one tuple containing both the manage_edit and Manager methods?

More generally, where can I find a REFERENCE doc (instead of a collection of
how-tos or other items more or less related to the topic which is
interesting you) in which such information (I mean developping Python code
for Zope products) is __clearly__ defined?

Thanks a lot in advance,

Philippe