Abordagem evitando o relacionamento ternário.

models_exp.py

"""
>>> rsp = models.Journal.objects.create(title=u'Revista de saúde pública')
(0.002) INSERT INTO "journalmanager_journal" ("title") VALUES (Revista de saúde pública); args=[u'Revista de sa\xfade p\xfablica']
>>>
>>> brasil = models.Collection.objects.create(name=u'Brasil')
(0.001) INSERT INTO "journalmanager_collection" ("name") VALUES (Brasil); args=[u'Brasil']
>>>
>>> rsp.join(brasil)
(0.001) INSERT INTO "journalmanager_membership" ("journal_id", "collection_id", "publication_status", "publication_status_since") VALUES (1, 1, c, 2014-03-22 22:47:59.174742); args=[1, 1, 'c', u'2014-03-22 22:47:59.174742']
(0.001) INSERT INTO "journalmanager_journaltimeline" ("journal_id", "collection_id", "publication_status", "publication_status_since") VALUES (1, 1, c, 2014-03-22 22:47:59.174742); args=[1, 1, 'c', u'2014-03-22 22:47:59.174742']
>>>
>>> rsp.change_status(brasil, 'd')
(0.000) SELECT "journalmanager_membership"."id", "journalmanager_membership"."journal_id", "journalmanager_membership"."collection_id", "journalmanager_membership"."publication_status", "journalmanager_membership"."publication_status_since" FROM "journalmanager_membership" WHERE ("journalmanager_membership"."journal_id" = 1  AND "journalmanager_membership"."collection_id" = 1 ); args=(1, 1)
(0.000) SELECT (1) AS "a" FROM "journalmanager_membership" WHERE "journalmanager_membership"."id" = 1  LIMIT 1; args=(1,)
(0.001) UPDATE "journalmanager_membership" SET "journal_id" = 1, "collection_id" = 1, "publication_status" = d, "publication_status_since" = 2014-03-22 22:48:15.571127 WHERE "journalmanager_membership"."id" = 1 ; args=(1, 1, 'd', u'2014-03-22 22:48:15.571127', 1)
(0.000) SELECT "journalmanager_journal"."id", "journalmanager_journal"."title" FROM "journalmanager_journal" WHERE "journalmanager_journal"."id" = 1 ; args=(1,)
(0.000) SELECT "journalmanager_collection"."id", "journalmanager_collection"."name" FROM "journalmanager_collection" WHERE "journalmanager_collection"."id" = 1 ; args=(1,)
(0.000) INSERT INTO "journalmanager_journaltimeline" ("journal_id", "collection_id", "publication_status", "publication_status_since") VALUES (1, 1, d, 2014-03-22 22:48:15.571127); args=[1, 1, 'd', u'2014-03-22 22:48:15.571127']
>>>
>>> rsp.membership_info(brasil, 'publication_status')
(0.000) SELECT "journalmanager_membership"."id", "journalmanager_membership"."journal_id", "journalmanager_membership"."collection_id", "journalmanager_membership"."publication_status", "journalmanager_membership"."publication_status_since" FROM "journalmanager_membership" WHERE ("journalmanager_membership"."journal_id" = 1  AND "journalmanager_membership"."collection_id" = 1 ); args=(1, 1)
u'd'
>>>
>>> rsp.statuses.all()
(0.000) SELECT "journalmanager_journaltimeline"."id", "journalmanager_journaltimeline"."journal_id", "journalmanager_journaltimeline"."collection_id", "journalmanager_journaltimeline"."publication_status", "journalmanager_journaltimeline"."publication_status_since" FROM "journalmanager_journaltimeline" WHERE "journalmanager_journaltimeline"."journal_id" = 1  LIMIT 21; args=(1,)
[<JournalTimeline: JournalTimeline object>, <JournalTimeline: JournalTimeline object>]
"""
from django.db import models


class Journal(models.Model):
    collections = models.ManyToManyField('Collection',
        through='Membership', related_name='journals')
    title = models.CharField(max_length=32)

    def join(self, collection):
        """Make this journal part of the collection.
        """

        Membership.objects.create(journal=self,
                                  collection=collection,
                                  publication_status='c')

    def membership_info(self, collection, attribute=None):
        """Retrieve info about the relation of this journal with a
        given collection.
        """
        rel = self.membership_set.get(collection=collection)
        if attribute:
            return getattr(rel, attribute)
        else:
            return rel

    def change_status(self, collection, new_status):
        rel = self.membership_info(collection)
        rel.publication_status = new_status
        rel.save()


class Collection(models.Model):
    name = models.CharField(max_length=32)

    def add_journal(self, journal):
        journal.join(self)


class Membership(models.Model):
    """
    Represents the many-to-many relation
    between Journal and Collection.
    """
    journal = models.ForeignKey('Journal')
    collection = models.ForeignKey('Collection')

    publication_status = models.CharField(max_length=1,
        choices=[('c', 'current'), ('d', 'deceased')])
    publication_status_since = models.DateTimeField(auto_now=True)

    def save(self, *args, **kwargs):
        """
        Always save a copy at JournalTimeline
        """
        super(Membership, self).save(*args, **kwargs)
        JournalTimeline.objects.create(journal=self.journal,
                                       collection=self.collection,
                                       publication_status=self.publication_status,
                                       publication_status_since=self.publication_status_since)

class JournalTimeline(models.Model):
    """
    Represents the status history of a journal.
    """
    journal = models.ForeignKey('Journal', related_name='statuses')
    collection = models.ForeignKey('Collection')

    publication_status = models.CharField(max_length=1,
        choices=[('c', 'current'), ('d', 'deceased')])
    publication_status_since = models.DateTimeField()

Eu até tinha pensado nisso na hora que escrevi no papel, mas não soube explicar direito.

Eu acho que teremos que começar o model-overhaul do zero :-/ mas tudo bem.

faz parte =]