--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/book/devrepo/entityclasses/data-as-objects.rst	Thu Jan 08 22:11:06 2015 +0100
@@ -0,0 +1,142 @@
+Access to persistent data
+--------------------------
+
+Python-level access to persistent data is provided by the
+:class:`Entity <cubicweb.entity>` class.
+
+.. XXX this part is not clear. refactor it.
+
+An entity class is bound to a schema entity type. Descriptors are added when
+classes are registered in order to initialize the class according to its schema:
+
+* the attributes defined in the schema appear as attributes of these classes
+
+* the relations defined in the schema appear as attributes of these classes,
+  but are lists of instances
+
+`Formatting and output generation`:
+
+* :meth:`view(__vid, __registry='views', **kwargs)`, applies the given view to the entity
+  (and returns a unicode string)
+
+* :meth:`absolute_url(*args, **kwargs)`, returns an absolute URL including the base-url
+
+* :meth:`rest_path()`, returns a relative REST URL to get the entity
+
+* :meth:`printable_value(attr, value=_marker, attrtype=None, format='text/html', displaytime=True)`,
+  returns a string enabling the display of an attribute value in a given format
+  (the value is automatically recovered if necessary)
+
+`Data handling`:
+
+* :meth:`as_rset()`, converts the entity into an equivalent result set simulating the
+  request `Any X WHERE X eid _eid_`
+
+* :meth:`complete(skip_bytes=True)`, executes a request that recovers at
+  once all the missing attributes of an entity
+
+* :meth:`get_value(name)`, returns the value associated to the attribute name given
+  in parameter
+
+* :meth:`related(rtype, role='subject', limit=None, entities=False)`,
+  returns a list of entities related to the current entity by the
+  relation given in parameter
+
+* :meth:`unrelated(rtype, targettype, role='subject', limit=None)`,
+  returns a result set corresponding to the entities not (yet)
+  related to the current entity by the relation given in parameter
+  and satisfying its constraints
+
+* :meth:`cw_set(**kwargs)`, updates entity's attributes and/or relation with the
+  corresponding values given named parameters. To set a relation where this
+  entity is the object of the relation, use `reverse_<relation>` as argument
+  name.  Values may be an entity, a list of entities, or None (meaning that all
+  relations of the given type from or to this object should be deleted).
+
+* :meth:`copy_relations(ceid)`, copies the relations of the entities having the eid
+  given in the parameters on the current entity
+
+* :meth:`cw_delete()` allows to delete the entity
+
+
+The :class:`AnyEntity` class
+----------------------------
+
+To provide a specific behavior for each entity, we can define a class
+inheriting from `cubicweb.entities.AnyEntity`. In general, we define this class
+in `mycube.entities` module (or in a submodule if we want to split code among
+multiple files) so that it will be available on both server and client side.
+
+The class `AnyEntity` is a sub-class of Entity that add methods to it,
+and helps specializing (by further subclassing) the handling of a
+given entity type.
+
+Most methods defined for `AnyEntity`, in addition to `Entity`, add
+support for the `Dublin Core`_ metadata.
+
+.. _`Dublin Core`: http://dublincore.org/
+
+`Standard meta-data (Dublin Core)`:
+
+* :meth:`dc_title()`, returns a unicode string corresponding to the
+  meta-data `Title` (used by default is the first non-meta attribute
+  of the entity schema)
+
+* :meth:`dc_long_title()`, same as dc_title but can return a more
+  detailed title
+
+* :meth:`dc_description(format='text/plain')`, returns a unicode string
+  corresponding to the meta-data `Description` (looks for a
+  description attribute by default)
+
+* :meth:`dc_authors()`, returns a unicode string corresponding to the meta-data
+  `Authors` (owners by default)
+
+* :meth:`dc_creator()`, returns a unicode string corresponding to the
+  creator of the entity
+
+* :meth:`dc_date(date_format=None)`, returns a unicode string corresponding to
+  the meta-data `Date` (update date by default)
+
+* :meth:`dc_type(form='')`, returns a string to display the entity type by
+  specifying the preferred form (`plural` for a plural form)
+
+* :meth:`dc_language()`, returns the language used by the entity
+
+Inheritance
+-----------
+
+When describing a data model, entities can inherit from other entities as is
+common in object-oriented programming.
+
+You have the possibility to redefine whatever pleases you, as follow:
+
+.. sourcecode:: python
+
+    from cubes.OTHER_CUBE import entities
+
+    class EntityExample(entities.EntityExample):
+
+        def dc_long_title(self):
+            return '%s (%s)' % (self.name, self.description)
+
+The most specific entity definition will always the one used by the
+ORM. For instance, the new EntityExample above in mycube replaces the
+one in OTHER_CUBE. These types are stored in the `etype` section of
+the `vregistry`.
+
+Notice this is different than yams schema inheritance, which is an
+experimental undocumented feature.
+
+
+Application logic
+-----------------
+
+While a lot of custom behaviour and application logic can be
+implemented using entity classes, the programmer must be aware that
+adding new attributes and method on an entity class adds may shadow
+schema-level attribute or relation definitions.
+
+To keep entities clean (mostly data structures plus a few universal
+methods such as listed above), one should use `adapters` (see
+:ref:`adapters`).