cvc-elt.1: Cannot find the declaration of element

Question

I'm trying to validate a really simple xml using xsd, but for some reason I get this error. I'll really appreciate if someone can explain me why.

XML File

<?xml version="1.0" encoding="utf-8"?> 
<MyElement>A</MyElement>

XSD File

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
        targetNamespace="http://www.example.org/Test"
        xmlns:tns="http://www.example.org/Test"
        elementFormDefault="qualified">

    <simpleType name="MyType">
        <restriction base="string"></restriction>
    </simpleType>

    <element name="MyElement" type="tns:MyType"></element>
</schema>

Answer 1

I had this error for my XXX element and it was because my XSD was wrongly formatted according to javax.xml.bind v2.2.11 . I think it's using an older XSD format but I didn't bother to confirm.

My initial wrong XSD was alike the following:

<xs:element name="Document" type="Document"/>
...
<xs:complexType name="Document">
    <xs:sequence>
        <xs:element name="XXX" type="XXX_TYPE"/>
    </xs:sequence>
</xs:complexType>

The good XSD format for my migration to succeed was the following:

<xs:element name="Document">
    <xs:complexType>
        <xs:sequence>
            <xs:element ref="XXX"/>
        </xs:sequence>
    </xs:complexType>        
</xs:element>
...
<xs:element name="XXX" type="XXX_TYPE"/>

And so on for every similar XSD nodes.

Answer 2

Your schema is for its target namespace http://www.example.org/Test so it defines an element with name MyElement in that target namespace http://www.example.org/Test. Your instance document however has an element with name MyElement in no namespace. That is why the validating parser tells you it can't find a declaration for that element, you haven't provided a schema for elements in no namespace.

You either need to change the schema to not use a target namespace at all or you need to change the instance to use e.g. <MyElement xmlns="http://www.example.org/Test">A</MyElement>.