Resolvers took the last message in a transaction. Wherever one party fixes
a message and another assembles the transaction - the delivery escrow pins
the registration at output 1 - a later output could replace it and every
resolver would read that one. Counting instead of choosing removes the
question: one message, or the transaction says nothing.
Same rule in all three resolvers. The Android parser now recognises the
same set of operations as the JavaScript one, since what counts as a
message decides which transactions are void. No transaction on chipnet
carried more than one.
Three older suites built registrations that never created their
certificate's category; their fixtures now do, as the sole-certificate
rule requires.
Ownership of a name is proven by holding a token of its category: an update
is accepted when some output carries it. Nothing required that the
certificate be the only such token. Whoever registered a name could mint a
second one in the same transaction, a minting token for instance, sell the
certificate on the market, and later publish an update the resolvers would
accept. The buyer would hold the certificate and lose the name.
A registration now counts only if its category is created by that very
transaction, exactly one output carries it, and that output is an NFT with
no capability and no fungible amount. Nothing meeting this can ever have a
sibling. The same holds for TLD certificates, whose category proves the
right to set a TLD's policy and to co-sign registrations under it.
One definition, in resolver-web.js; bns.js and the TLD snapshot builder call
it. Every valid registration on chipnet already satisfied the rule: the live
registry is the same 71 names and 21 TLDs before and after.
Found while writing the delivery escrow, which had to forbid exactly this.
