What's the meaning of "xsd:extension base = ....?

What's the meaning of ? Does SubParameter type included all the information of MainParameter.type content? and attribute MyIndex attached.

  <xsd:complexType name="SubParameter.type">
    <xsd:complexContent>
      <xsd:extension base="MainParameter.type">
        <xsd:attribute name="MyIndex"开发者_如何学Python type="xsd:nonNegativeInteger"/>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>

Thank you.

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You are declaring a type that extends MainParameter.type.

In other words, your new type "SubParameter.type" will have all the attributes and structure of MainParameter but with an additional MyIndex attribute.