intro.xml
<?xml version = "1.0"?>

<myMessage xmlns = "x-schema:intro-schema.xml">

   <message>This is the second message!
       <id>dd</id>
     </message>
   <greeting>Welcome to XML Schema!
     <message>This is the first message!</message>
     <new>ddddddd</new>
   </greeting>
     
   
</myMessage>

intro-schema.xml

  <?xml version = "1.0"?>

<!-- Fig. 7.1 : intro-schema.xml                  -->
<!-- Microsoft XML Schema showing the ElementType -->
<!-- element and element element                  -->

<Schema xmlns = "urn:schemas-microsoft-com:xml-data">
   <ElementType name = "message" content = "textOnly"
      model = "closed">
      <description>Text messages</description>
   </ElementType>

   <ElementType name = "greeting" model = "closed"
      content = "mixed" order = "many">
      <element type = "message"/>
   </ElementType>

   <ElementType name = "myMessage" model = "closed"
      content = "eltOnly" order = "seq">

      <element type = "greeting" minOccurs = "0"
         maxOccurs = "1"/>
      <element type = "message" minOccurs = "1"
         maxOccurs = "*"/>

   </ElementType>
</Schema>

问题如下：1。message元素我定义为textonly，为什么还可以包含<id>元素
               2。<ElementType name = "myMessage" model = "closed"
      content = "eltOnly" order = "seq">我定义为seq，为什么我这样排序也不会出错呢？