The default behavior for <foreign> is to try to display the
content. If the processor cannot render the content, it may emit a warning.
The default processing behavior for <unknown> is to suppress.
This section describes processing behaviour of specialized foreign content
based on existing standard vocabularies for non-textual content.
- Default processing for <foreign>
-
The enabler of the foreign vocabulary must provide the processing
by overriding the base processing for <foreign>.
- If <foreign> contains more than one alternative content element,
they will all be processed. In the case of <desc> they will be concatenated
in a similar way to <section> but no title (similar to <div> in
HTML).
- Where appropriate, the specializer may specialize a nested <desc>
element to provide alternate content that is valid in the contexts for the <foreign>
specialization. If an instance of the <foreign> element doesn't
contain a <desc>, <object>, or <image> element, the base
processing may emit a warning about the absence of processable content.
- If the instance of the <foreign> element doesn't contain a <desc>, <object>,
or <image> element, the base processing may emit a warning about the
absence of processable content.
- The base processing for <object> can emit the content of <foreign>
as a file at the location specified by the data attribute of the <object>
element. The <object> element should have a data attribute or an <foreign>
sub-element but not both. In the event that an <object> element contains
both a data attribute and an <foreign> sub-element the processing system
will ignore one of them.
- Default processing for <unknown>
-
The base processing for <unknown> is to suppress unless
otherwise instructed.