If your application is Twinnable, you may want to have some fields of a model common to all contexts. For example, in Monkey application, the birth year, species and photo of a monkey are not context dependants. A monkey in french version will have the same birth year, the same species and the same photo that in english version.
See also
For define a common field, just adds it to common_fields key of Twinnable behaviour.
<?php
class Model_Page extends \Nos\Orm\Model
{
protected static $_behaviours = array(
'Nos\Orm_Behaviour_Twinnable' => array(
'context_property' => 'monk_context',
'common_id_property' => 'monk_context_common_id',
'is_main_property' => 'monk_context_is_main',
'common_fields' => array('monk_species_common_id', 'monk_birth_year'),
),
);
}