确认过程根据文档类型定义(DTD)来检查XML, DTD可以是XML的一部分，也可以在它的外部。

The process of validation checks the XML against a Document Type Definition (DTD), which may be part of the XML or external to it.

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取而代之的是，这些类型信息是由外部机制提供的，更像使用XML schema来确切地定义SOAP消息中使用的类型的WSDL文档。

Instead, the type information is provided by an external mechanism, more likely than not a WSDL document that USES XML schema to define exactly what types are used in the SOAP message.

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