diff -r 78ad3da30e8a stdlibchanges.rst
--- a/stdlibchanges.rst	Sat Jan 02 09:11:24 2016 -0600
+++ b/stdlibchanges.rst	Tue Mar 22 18:15:16 2016 +0100
@@ -49,6 +49,34 @@
 
 .. _Python Cookbook: http://code.activestate.com/recipes/langs/python/
 
+Private vs. public API
+''''''''''''''''''''''
+If a module or package defines ``__all__`` that authoritatively defines the
+public interface. Modules with ``__all__`` SHOULD still respect the naming
+conventions (leading underscore for private members) to avoid confusing users.
+Modules SHOULD NOT export private members in ``__all__``.
+
+Names imported into a module a never considered part of its public API unless
+documented to be so or included in ``__all__``.
+
+Methods / functions / classes and module attributes whose names begin with a
+leading underscore are private.
+
+If a class name begins with a leading underscore none of its members are
+public, whether or not they begin with a leading underscore.
+
+If a module name in a package begins with a leading underscore none of its
+members are public, whether or not they begin with a leading underscore.
+
+If a module or package doesn't define ``__all__`` then all names that don't
+start with a leading underscore are public.
+
+All public members MUST be documented. Public functions, methods and classes
+SHOULD have docstrings. Private members may have docstrings.
+
+Where in the standard library this means that a module exports stuff that isn't
+helpful or shouldn't be part of the public API we need to migrate to private
+names and follow our deprecation process for the public names.
 
 Adding a new module
 -------------------