[XML Schema 1.1] <openContent> applies only to the children, not the grandchildren ... correct?

Hi Folks,

I want to confirm my understanding.

Consider this <Book> element with open content:

<element name="Book">
    <complexType>
        <openContent mode="interleaved">
            <any />
        </openContent>
        <sequence>
            <element name="Title" type="string"/>
            <element name="Author">
                <complexType>
                    <sequence>
                        <element name="FirstName" type="string"/>
                        <element name="LastName" type="string"/>
                    </sequence>
                </complexType>
            </element>
            <element name="Date" type="string"/>
            <element name="ISBN" type="string"/>
            <element name="Publisher" type="string"/>
        </sequence>
    </complexType>
</element>

Notice that the <Author> element has child elements, which are grandchildren of the <Book> element.

Extension elements can only be added before and after the *children* of Book. Extension elements cannot be added around the *grandchildren* of Book. Thus, extension elements cannot be added before or after <FirstName> and <LastName>.

Is this correct?

/Roger