The term is used many times on the whitepaper but I can't find a definition. What would be examples of a conflicting transaction?

Extract form Whitepaper:

The main idea of the tangle is the following: to issue a transaction, users must work to approve other transactions. Therefore, users who issue a transaction are contributing to the network’s security. It is assumed that the nodes check if the approved transactions are not conflicting. If a node finds that a transaction is in conflict with the tangle history, the node will not approve the conflicting transaction in either a direct or indirect manner³.

  • Please provide more context. A citation of an extract from the whitepaper, you don't understand due to the missing definition, would increase the quality of your Question a lot.
    – Tobi MZ
    Feb 25 '18 at 3:12
  • First appearance on final of page 2: "It is assumed that the nodes check if the approved transactions are not conflicting". Hence my question, what would that be?
    – user1710
    Feb 25 '18 at 3:17
  • make sure your questions fullfill the qualitystandards
    – Tobi MZ
    Feb 25 '18 at 3:23

Transactions are conflicting if they try to spend the same money from the same address (and the address does not include enough money to satisfy both at the same time - but this should not happen anyway, as compliant clients will move the remaining balance to a change address - but can of course happen if an adversary tries this).

Either this can be because there is a real double spend (e. g. somebody tried to send the same funds to two different addresses) or in case somebody reattaches their transactions (only one of the transfers can confirm then).

  • Can't we disallow spending the same money from the same address, by using some distributed mutual exclusion schemes?
    – D Mitra
    Sep 25 at 4:12
  • 1
    The answer was from before the Chrysalis update. With Chrysalis, UTXO and white-flagging are used to determine which one of the conflicting transactions wins, and so both can be confirmed. See iota.cafe/t/…
    – mihi
    Sep 26 at 8:57
  • I have one basic question, why are conflicting transactions temporarily allowed in tangle and later dealt with, why not deal with them using some safeguard mechanisms that prevents conflicting transactions spending from the same address. I am new to this topic, so my question may seem puerile.
    – D Mitra
    Oct 1 at 12:42
  • 1
    @DMitra The problem is the same as with any other distributed system: When a node receives a transaction it cannot now with certainty that another node has not yet received a conflicting transaction (which should take only seconds, but could take longer to get synchronized). And once a transaction is "in the tangle", you cannot easily remove it without affecting its descendants.
    – mihi
    Oct 1 at 16:43

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