SYMPTOMS
Validating an XML Document with MSXML gives the following error message:
0xC00CE01D. Reference to undeclared namespace prefix: 'xlink'.
STEPS TO REPRODUCE BEHAVIOR
1 - Start XMLBlueprint.
2 - Paste the following code into a new text document, and save the file as book.xml:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book SYSTEM "book.dtd">
<book>
<chapter xlink:href="http://www.xmlblueprint.com"/>
</book>
3 - Paste the following code into a new text document, and save the file as book.dtd in the same folder as book.xml:
<!ELEMENT book (chapter)*>
<!ATTLIST book xmlns:xlink CDATA #FIXED "http://www.w3.org/1999/xlink">
<!ELEMENT chapter (#PCDATA)>
<!ATTLIST chapter xlink:href CDATA #IMPLIED>
4 - Open file book.xml and validate by clicking XML > Validate. The error message will appear in the Output Window.
SOLUTION
To avoid this error, change <book> to <book xmlns:xlink="http://www.w3.org/1999/xlink">:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book SYSTEM "book.dtd">
<book xmlns:xlink="http://www.w3.org/1999/xlink">
<chapter xlink:href="http://www.xmlblueprint.com"/>
</book>