In this case, the XML data file contains the location of the DTD file. It looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE TABLE1 SYSTEM "DTD_file_name_including_the_complete_path">
...
This entry is needed for the XML parser to locate the DTD and validate against it if required. It is optional if you do not choose to validate your data source.
About document type definition (DTD) formats
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