How do I use inheritance (ie xs:extension) in my own xml schema?

I'm trying to make my own xml schema in Visual Studio. But I can't make any complex types such as a Rectangle type, nor inheritable types such as Shape. The schema.xsd follows and the errors I'm getting are :

1. Namespace '' is not available to be referenced in this schema. [line 6 xs:extension base="Shape">

2. Undefined complexType 'Shape' is used as a base for complex type extension [line 6 again ]

Content:

<?xml version="1.0" encoding="utf-8"?>
<xs:schema 
    attributeFormDefault="unqualified" 开发者_C百科
    elementFormDefault="qualified" 
    xmlns:xs  ="http://www.w3.org/2001/XMLSchema" 
    targetNamespace="MySchema">

<xs:complexType name="Rectangle">
 <xs:complexContent>
   <xs:extension base="Shape">
     <xs:sequence>
      <xs:element minOccurs="0" name ="X" type="xs:int"/>
      <xs:element minOccurs="0" name ="Y" type="xs:int"/>
      <xs:element minOccurs="0" name ="Width" type="xs:int"/>
      <xs:element minOccurs="0" name ="Height" type="xs:int"/>
    </xs:sequence>
   </xs:extension>
 </xs:complexContent>

</xs:complexType>
<xs:complexType name="Shape">
  <xs:sequence>
    <xs:element name="Complexity" type="xs:string"/>
  </xs:sequence>  
</xs:complexType>

---

You need to bind a prefix to the target namespace:

xmlns:m="MySchema"

and use this in references to components defined within the schema

base="m:Shape"

---

To resolve Namespace '' is not available to be referenced in this schema. You can set the default '' namespace without the need to change the rest of the file:

Add this xmlns="MySchema"

<?xml version="1.0" encoding="utf-8"?> 
<xs:schema  
    attributeFormDefault="unqualified"  
    elementFormDefault="qualified"  
    xmlns:xs  ="http://www.w3.org/2001/XMLSchema"  
    xmlns="MySchema"
    targetNamespace="MySchema"> 
...