http://docs.djangoproject.com/en/dev/ref/contrib/syndication/
"
To specify the contents of <link>, you have two options. For each item in items(), Django first tries executing a get_absolute_url() method on that object. If that method doesn't exist, it tries calling a method item_link() in the Feed class, passing it a single parameter, item, which is the object itself.
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and
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# ITEM LINK -- One of these three is required. The framework looks for
# them in this order.
# First, the framework tries the two methods below, in
# order. Failing that, it falls back to the get_absolute_url()
# method on each item returned by items().
"
they tell us two different orders. according to my test, the latter is correct.