What kind of content is allowed in simple types & simple content?

Hi,

If an XML element is declared as simpleType of with simpleContent in XML 
Schema, is it then valid even with nested comments and processing 
instrtuctions?

Like:

<element name="foo">
<simpleType>
<restriction base="string">
<enumeration value="Du bist Schuld, nicht die Kanone!"/>
</restriction>
</simpleType>
</element>

<foo>Du bist Schuld<!--stupid comment-->, nicht<?foo bar?> die Kanone!</foo>

Soren