from django.db import models

from django.contrib.auth.models import *

class Owner(models.Model):

    user = models.ForeignKey(User,  blank=True, null=True)

    group = models.ForeignKey(Group,  blank=True, null=True)

    def __unicode__(self):

        if self.user:

            return self.user.username

        else:

            return self.group.name

class Document(models.Model):

    owner= models.ForeignKey(Owner, blank = True, null=True)

    class Meta:

        abstract = True