There is no “null” in standard syntax. For an empty select_one, you would use “” (or ‘’), i.e. empty string. You might also use count-selected(…) = 0. See ODK XForms Specification.
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There is no “null” in standard syntax. For an empty select_one, you would use “” (or ‘’), i.e. empty string. You might also use count-selected(…) = 0. See ODK XForms Specification.