208 class ExternalUri(EntityType):

   209     """a URI representing an object in external data store"""

   210     uri = String(required=True, unique=True, maxsize=256,

   211                  description=_('the URI of the object'))

   212 

   213 class same_as(RelationType):

   214     """generic relation to specify that an external entity represent the same

   215     object as a local one:

   216        http://www.w3.org/TR/owl-ref/#sameAs-def

   217 

   218     NOTE: You'll have to explicitly declare which entity types can have a

   219     same_as relation

   220     """

   221     permissions = {

   222         'read':   ('managers', 'users', 'guests',),

   223         'add':    ('managers', 'users'),

   224         'delete': ('managers', 'owners'),

   225         }

   226     cardinality = '*1'

   227     symetric = True

   228     # NOTE: the 'object = ExternalUri' declaration will still be mandatory

   229     #       in the cube's schema.

   230     object = 'ExternalUri'