一般情况下，DOM实现必须检验操作的正确性，并在应用程序传递错误参数或者执行非法操作时抛出异常。

Normally, a DOM implementation must verify the correctness of operations and throw an exception if an application passes the wrong parameters or performs an illegal operation.

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某个活动的多次出现，不一定会导致流程执行错误，但是它会影响模型的可读性。

Multiple occurrences of an activity do not necessarily lead to a process execution error, but they can affect the readability of the model.

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还需要能够跟着错误和程序输出，并需要能够确保脚本的执行环境的安全性和有效性。

You also need to be able to trap errors and output from programs and ensure the security and validity of the environment in which the script executes.

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