Strategy: Types are the basis of re-use and not elements.

Make all your types (complex & simple) global.

The exceptions:

• Children that are lists of other elements:

  <xs:complexType name="department">
  <xs:sequence>
     <xs:element name="xs:string"/>
     <xs:element name="people">
        <xs:complexType>
           <xs:sequence>
              <xs:element ref="my:person" maxOccurs="unbounded"/>
           </xs:sequence>
        </xs:complexType>
     </xs:element>
  </xs:sequence>
  </xs:complexType>

• Any element who's type can be justified as always being "local" to that element (a slippery slope):

  <xs:complexType name="pipeline">
  <xs:sequence>
     <xs:element name="version-information" minOccurs="0">
        <xs:complexType mixed="true">
            <xs:sequence>
               <xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
            </xs:sequence>
            <xs:anyAttribute processContents="lax"/>
        </xs:complexType>
     </xs:element>
  </xs:sequence>
  </xs:complexType>