<?xml version="1.0"?> <!DOCTYPE concept SYSTEM "concept.dtd"> <concept id="topicid"> <title>Test concept</title> </concept>
Modify the system identifier (the part in bold) to reflect the actual location of the shell DTD relative to the test document.
Remember that in XML all system identifiers are URIs, meaning you're specifying a URL, not a system-specific file path. So no backslashes if you're on Windows.
Validate this document. It should be valid at this point as you haven't modified the document type shell file in any way.