Error: The prefix "xsd" for element "xsd:schema" is not bound

Question

I'm extremely new to XML, and currently ready Ineasysteps. I keep getting the same issue from the parser saying

5:The prefix "xsd" for element "xsd:schema" is not bound.

This is the hello.xml:

<?xml version = "1.0" encoding = "UTF-8" ?>

<!-- XML in easy steps - Page 82. -->

<doc xmlns:xsi=
"http://www.w3.org/2001/XMLSchema-instance" 
xsi:noNamespaceSchemaLocation = "hello.xsd" >

<msg>Hello World</msg>

</doc>

Here is the hello.xsd doc

<?xml version="1.0" encoding = "UTF-8" ?>

<!-- XML in easy steps - Page 84. -->

<xsd:schema>

<!-- DECLARE ELEMENTS. -->  

<!-- Simple types. -->
<xsd:element name="msg" type="xsd:string"/>

 <!-- Complex types. -->
 <xsd:element name="doc" type="docType"/>

<!-- DEFINE STRUCTURE. -->

<xsd:complexType name="docType">
<xsd:sequence>
    <xsd:element ref="msg"/>
</xsd:sequence>
</xsd:complexType

Answer 1

A namespace prefix such as xsd must be defined before being used. This applies even to the well-known xsd (or xs) prefixes commonly used for the component of XML Schema (XSD).

To eliminate the error, define the xsd namespace prefix by adding

xmlns:xsd="http://www.w3.org/2001/XMLSchema"

to the xsd:schema root element like this:

<?xml version="1.0" encoding = "UTF-8" ?>
<!-- XML in easy steps - Page 84. -->
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

  <!-- DECLARE ELEMENTS. -->  

  <!-- Simple types. -->
  <xsd:element name="msg" type="xsd:string"/>

  <!-- Complex types. -->
  <xsd:element name="doc" type="docType"/>

  <!-- DEFINE STRUCTURE. -->

  <xsd:complexType name="docType">
    <xsd:sequence>
      <xsd:element ref="msg"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:schema>