Is transaction validity the validity of the binary from the point of view of the write node?

I think valid It is generally a somewhat vague term. On the one hand, nodes validate transactions using a list of criteria. If all criteria are met, the transaction is considered valid. One such criteria is:For each input, there must be an output to be referenced and is not available yet” (Anthonopoulos, Bitcoin Masterp. 235). Therefore, if all inputs in a new transaction are UTXOS, the criteria are checked.

At the same time, when discussing “51% attacks,” Antonopoulos states:The more confirmations you get, the more difficult it will be to disable transactions with 51% of attacks.This means that chain reorganization can invalidate transactions.

Therefore, from the miner’s perspective, transaction validity is a binary property. However, from a broader network perspective, it is probabilistic.