Conformance: valid root vs valid document (ODF 1.2 CD01)

Dear all,

1.4.2.1 ("Conforming OpenDocument Documents"), D1.2.3 has this:

"If the XML root element of a sub document is <office:document-content>,
<office:document-styles>, <office:document-meta> or
<office:document-settings>, then the XML root element shall be valid
with respect to the strict schema defined by this specification."

* Is it just the root element that shall be valid, or is the entire
document intended here?

* What is "the strict schema" ?

- Alex.