在不同的系统之间转移文件时，文件名和扩展名常常是随着一起移动的唯一元数据。

When files are moved between heterogeneous systems, the name and the extension are often the only metadata that move with them.

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对于在本地文件系统上打开的文件，浏览器根据文件的扩展名来猜测MIME类型。

For files opened from your local file system, the browser guesses the MIME type based on the file's extension.

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如果在文件系统中存储XML文档，应使用标准的文件扩展名。

If you store XML documents in a file system, use a standard file extension.

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