Directives passed to put() and add() handlers for guiding the update and creation of stored objects.
If the collection of objects in the store has a natural ordering, this indicates that the created or updated object should be placed before the object specified by the value of this property. A value of null indicates that the object should be last.
If this is provided as a boolean it indicates that the object should or should not overwrite an existing object. A value of true indicates that a new object should not be created, the operation should update an existing object. A value of false indicates that an existing object should not be updated, a new object should be created (which is the same as an add() operation). When this property is not provided, either an update or creation is acceptable.
If the store is hierarchical (with single parenting) this property indicates the new parent of the created or updated object.