This is a standard XML header with a reference to the format description file. The header should start from the first line, with the null character.
The second line of the XML document header references the XML DTD file. It is sufficient to specify the file name shops.dtd without the path, since the file is located on the Yandex.Market side.
<?xml version="1.0" encoding="windows-1251"?> <!DOCTYPE yml_catalog SYSTEM "shops.dtd">