channel ItemRegistration {
	out inventory(itemDB:Map, registerItem(itemId:Str, itemName:Str, quantity:Int)) = insert(itemDB, itemId, {"count": quantity, "name": itemName})
}

channel Receiving(itemId:Str) {
	out inventory.{itemId}.count(prev_quantity:Int, receive(quantity:Int)) = prev_quantity + quantity
}

channel Shipping(itemId:Str) {
	out inventory.{itemId}.count(prev_quantity:Int, ship(quantity:Int)) = prev_quantity - quantity
}