The envelope contains an optional Header and a mandatory Body.

信封包含可选的Header和必需的Body。

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The envelope element contains a body element and an optional header element.

信封元素包含一个 body 元素和一个可选的 header 元素。

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The SOAP specification describes that a SOAP envelope can contain an optional header part.

SOAP规范描述了SOAP信封可以包括一个可选的消息头部分。

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In the text payload, a section called UDH (User Data Header) is optional but defines lot of advanced features not all mobiles are compatible with.

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