[Zope3-Users] schema interface field validation

[Alen Stanisic]

Hi,

could I reference other fields inside the schema interface to, for
example, 
default one field based on the value entered in one of the previous
fields, 
or to set 'required' attribute based on previous fields entered 

for example if I had

field1 = TextLine(
	title = _("Field1"),
	description = _(u"Field1")
	required = "False")

field2 = TextLine(
	title = _("Field2"),
	description = _(u"Field2")
	required = ????)

and field2 is only required if field1 has not been entered,

or should this be handled elsewhere, maybe Views or Vocabularies.

Thanks
Alen