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diff --git a/src/mailman/interfaces/chain.py b/src/mailman/interfaces/chain.py
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+++ b/src/mailman/interfaces/chain.py
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+# Copyright (C) 2007-2009 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+# more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Interfaces describing the basics of chains and links."""
+
+from __future__ import absolute_import, unicode_literals
+
+__metaclass__ = type
+__all__ = [
+    'IChain',
+    'IChainIterator',
+    'IChainLink',
+    'IMutableChain',
+    'LinkAction',
+    ]
+
+
+from munepy import Enum
+from zope.interface import Interface, Attribute
+
+
+
+class LinkAction(Enum):
+    # Jump to another chain.
+    jump = 0
+    # Take a detour to another chain, returning to the original chain when
+    # completed (if no other jump occurs).
+    detour = 1
+    # Stop processing all chains.
+    stop = 2
+    # Continue processing the next link in the chain.
+    defer = 3
+    # Run a function and continue processing.
+    run = 4
+
+
+
+class IChainLink(Interface):
+    """A link in the chain."""
+
+    rule = Attribute('The rule to run for this link.')
+
+    action = Attribute('The LinkAction to take if this rule matches.')
+
+    chain = Attribute('The chain to jump or detour to.')
+
+    function = Attribute(
+        """The function to execute.
+
+        The function takes three arguments and returns nothing.
+        :param mlist: the IMailingList object
+        :param msg: the message being processed
+        :param msgdata: the message metadata dictionary
+        """)
+
+
+
+class IChain(Interface):
+    """A chain of rules."""
+
+    name = Attribute('Chain name; must be unique.')
+    description = Attribute('A brief description of the chain.')
+
+    def get_links(mlist, msg, msgdata):
+        """Get an `IChainIterator` for processing.
+
+        :param mlist: the IMailingList object
+        :param msg: the message being processed
+        :param msgdata: the message metadata dictionary
+        :return: An `IChainIterator`.
+        """
+
+
+
+class IChainIterator(Interface):
+    """An iterator over chain rules."""
+
+    def __iter__():
+        """Iterate over all the IChainLinks in this chain.
+
+        :return: an IChainLink.
+        """
+
+
+
+class IMutableChain(IChain):
+    """Like `IChain` but can be mutated."""
+
+    def append_link(link):
+        """Add a new chain link to the end of this chain.
+
+        :param link: The chain link to add.
+        """
+
+    def flush():
+        """Delete all links in this chain."""