select wheel from /test/oo/car
/**
output()
matchcount("wheel._ref.len",4,1)
**/
;

update /test/oo/car set wheel = wheel - ['Wheel:wheel2'] where id='Car:car1'
;

/**
sleep(1s)
**/
;

select wheel from /test/oo/car
/**
output()
matchcount("wheel._ref.len",3,1)
**/
;