All data has a life cycle. The longer the life cycle, the more energy required. The life cycle ends and the data will be deleted. This can eliminate useless data.
The life cycle of log data is a fixed year. Through the data life, the log write time can be calculated. The cross-chain read will compare this time with the block time. If it is greater than n * 5 minutes (n is Logical distance between the two chains), the log data is valid. In order to achieve reliable cross-chain data reading.