Metadata
--------

.. index::
   schema: meta-data;
   schema: eid; creation_date; modification_data; cwuri
   schema: created_by; owned_by; is; is_instance;

Each entity type in |cubicweb| has at least the following meta-data attributes and relations:

`eid`
  entity's identifier which is unique in an instance. We usually call this identifier `eid` for historical reason.

`creation_date`
  Date and time of the creation of the entity.

`modification_date`
  Date and time of the latest modification of an entity.

`cwuri`
  Reference URL of the entity, which is not expected to change.

`created_by`
  Relation to the :ref:`users <CWUser>` who has created the entity

`owned_by`
  Relation to :ref:`users <CWUser>` whom the entity belongs; usually the creator but not
  necessary, and it could have multiple owners notably for permission control

`is`
  Relation to the :ref:`entity type <CWEType>` of which type the entity is.

`is_instance`
  Relation to the :ref:`entity types <CWEType>` of which type the
  entity is an instance of.