What does "When using <simpleContent> mean the base type must be a complex type whose content type is simple ..." even means?

Question

Here is all the error that I continue to get from photocopiers ....

When <simpleContent> is used, the base type must be a complexType whose content type 
is simple, or, only if restriction is specified, a complex type with mixed content
and emptiable particle, or, only if extension is specified, a simple type.
'string' satisfies none of these conditions.

I thought I understood this, but, having received it several times, I must have lost it, who has a good “turn” on it

I narrowed it down to this element

<xs:element name="Note">
  <xs:complexType>
    <xs:simpleContent>
      <xs:restriction base="xs:string">
      </xs:restriction>
    </xs:simpleContent>
  </xs:complexType>
</xs:element>

I think I just played a major role in the project ...

Answer 1

,

<xs:extension base="xs:string">

<xs:restriction base="xs:string">

. . XML-: , .

, Note. , , , , Note / , / .