[Zope] - External Method questions

[David Ascher]

* I'd like to add an external method in a Shared package, but I'm not sure
  how to do it -- in the Add External Method form, what's the "module
  name", is it packagename.modulename, packagename/modulename, or what?
  I've tried various combinations with no luck.

* I want to return an image from my external method.  What I have
  which sort of works is:

	def foo(self, RESPONSE):
	    RESPONSE['content-type'] = 'image/png'
	    return mkimage()

  where mkimage returns the actual PNG image data.  Is this correct?

* How can an external method refer to the objects in the Zope app?
  'self' above is App -- can I do App.foo and get to object foo?

* Is there a way for external methods to read from files on the
  filesystem?  How about write to files on the filesystem?  What kinds of
  sandbox is in place?

--david