Cannot find the declaration of element 'assignments'

Question

So I am beginning with XML and Schemas and I ran across this today and I have not been able to figure it out.

I am getting and error that says,

Ln 5 Col 2 : Cannot find the declaration of element 'assignments'.

I believe I have declared the element, but perhaps I am missing something and have not.

This is my XML file:

<?xml version="1.0" encoding="UTF-8"?>
<assignments
    xmlns="http://www.w3.org/2001/XMLSchema-instance"
    SchemaLocation="A3.xsd"
>
    <assignment id="a1">
     <name>Schemas</name>
     <page>110</page>
    </assignment>

    <assignment id="a2">
     <name>Namespaces</name>
     <page>258</page>
     <files>names.xml</files>
     <files>names.dtd</files>
    </assignment>

    <assignment id="a3">
     <name>RELAX NG</name>
     <page>305</page>
     <files>account.xml</files>
     <files>customers.xml</files>
     <files>finance.xsd</files>
    </assignment>

</assignments>

This is my Schema file:

<?xml version="1.0" encoding="UTF-8"?>
<schema 
    xmlns="http://www.w3.org/2001/XMLSchema" 
    xmlns:target="http://www.levijackson.net/web340/ns" 
    targetNamespace="http://www.levijackson.net/web340/ns" elementFormDefault="qualified"
>
<element name="assignments" type="target:TypeAssignments"></element>

<complexType name="TypeAssignments">
    <sequence>
     <element name="assignment" type="target:assignmentInfo"></element>
    </sequence>
    <attribute name="id" type="string" use="required"/>
</complexType>

<complexType name="assignmentInfo">
    <sequence>
      <element name="name" type="string"></element>
      <element name="page" type="target:TypePage"></element>
      <element name="file" type="target:TypeFile" minOccurs="0" maxOccurs="unbounded"></element>
    </sequence>
</complexType>

<simpleType name="TypePage">
    <restriction base="integer">
     <minInclusive value="50" />
     <maxInclusive value="498" />
    </restriction>
</simpleType>

<simpleType name="TypeFile">
    <restriction base="string">
     <enumeration value=".xml" />
     <enumeration value=".dtd" />
     <enumeration value=".xsd" />
    </restriction>
</simpleType>

</schema>

As I am still learning, feel free to point out any other mistakes I may have made not related to the problem.

Thanks
Levi

Answer 1

Try the following. I took out some of the extra details of the schema element, but with a little tweaking something like the following should work:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;        
  <xs:element name="assignments" type="TypeAssignments" />    
  <xs:complexType name="TypeAssignments">
    <xs:sequence>
      <xs:element name="assignment" type="assignmentInfo" 
          minOccurs="0" maxOccurs="unbounded" />
    </xs:sequence>        
  </xs:complexType>

  <xs:complexType name="assignmentInfo">
    <xs:sequence>
      <xs:element name="name" type="xs:string" />
      <xs:element name="page" type="TypePage" />
      <xs:element name="files" type="xs:string"  minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:attribute name="id" type="xs:string" use="required" />
  </xs:complexType>   

  <xs:simpleType name="TypePage">
    <xs:restriction base="xs:integer">
      <xs:minInclusive value="50" />
      <xs:maxInclusive value="498" />
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="TypeFile">
    <xs:restriction base="xs:string">
      <xs:enumeration value=".xml" />
      <xs:enumeration value=".dtd" />
      <xs:enumeration value=".xsd" />
    </xs:restriction>
  </xs:simpleType>
</xs:schema>

Notes:

1. The ID attribute has been moved from TypeAssignments to assignmentInfo.
2. All types and element names have been prefixed with the namespace xs
3. I've added the minOccurs and maxOccurs attributes for the assignment elements. Otherwise, only a single assignment element is allowed within assignments.
4. I've auto-closed your elements using "/>" instead of "" Not necessary, but a bit less typing to do.

All in all, I didn't modify all that much so you have the right idea.

Answer 2

In your instance document, as excerpted above, you define the xmlns attribute on the <assignments> element, and do not elsewhere define a namespace. This means that the namespace of <assignments> and all of its descendents is set to "http://www.w3.org/2001/XMLSchema-instance".

Your schema document, however, specifies a targetNamespace value of "http://www.levijackson.net/web340/ns". Since the elements in your instance document does not have this namespace, validation fails.

Start by changing your instance document to look like this:

<assignments
    xmlns="http://www.levijackson.net/web340/ns"

Answer 3

The solution to this problem was that I was not declaring my main element 'assignments' as a complex element, I actually wasn't declaring it as anything at all.

So by taking this line from my schema file:

<element name="assignment" type="target:assignmentInfo" minOccurs="0" maxOccurs="unbounded"></element>

and changing it into this:

<element name="assignments">
    <complexType>
     <sequence>
      <element name="assignment" type="target:assignmentInfo" minOccurs="0" maxOccurs="unbounded"></element>
     </sequence>
    </complexType>
</element>

The element was properly defined, thanks for the help everyone.

Levi