Blockchain, cross-chain, and multi-chain

in a cross blockchain transaction, we assume that the transaction result can be a value transfer or the execution of a contract, and that • underlying networks are secure with a concept of transaction finality within a finite time, after which the transactions cannot be rolled back • we loosely use “value” as a generic term to represent the cryptographic object that the blockchain carries • security aspects such as double spending and 51 • we do not consider the semantics of data and exchange rate between two different tokens