foo should not have text (all data is in attributes)

Some elements express their data in enclosed text, for example:

<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>

Others express their data in attributes, for example:

<link href="http://example.org/"/>

This may create confusion.

Check the specification (example) for the correct way to encode this element.