+ validates_presence_of :id, :on => :update
+ validates_presence_of :changeset_id,:version, :timestamp
+ validates_uniqueness_of :id
+ validates_inclusion_of :visible, :in => [ true, false ]
+ validates_numericality_of :changeset_id, :version, :integer_only => true
+ validates_numericality_of :id, :on => :update, :integer_only => true
+ validates_associated :changeset