+ def empty_collection_uuid
+ 'd41d8cd98f00b204e9800998ecf8427e+0'
+ end
+
+ def empty_collection
+ if not $empty_collection
+ act_as_system_user do
+ ActiveRecord::Base.transaction do
+ $empty_collection = Collection.
+ where(uuid: empty_collection_uuid).
+ first_or_create!(manifest_text: '')
+ Link.where(tail_uuid: anonymous_group.uuid,
+ head_uuid: empty_collection_uuid,
+ link_class: 'permission',
+ name: 'can_read').first_or_create!
+ end
+ end
+ end
+ $empty_collection
+ end