xsd报错，the prefix "xml" cannot be bound to any namespace other its usual .该怎么解决

xsd报错，the prefix "xml" cannot be bound to any namespace other its usual ...
<xsd:schema xmlns="http://www.w3.org/XML/1998/namespace" 
  targetNamespace="http://www.w3.org/XML/1998/namespace" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  elementFormDefault="qualified">
报错如下
The prefix "xml" cannot be bound to any namespace other than its usual namespace; neither can the namespace for "xml" be bound to any prefix other than "xml".
请高人指点指点

------解决方案--------------------
<xsd:schema 
targetNamespace="http://www.w3.org/XML/1998/namespace" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="qualified">

或者干脆

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified">