it seems that duplicate element and attribute declarations in DTDs are not recognized by Notepad++ as errors (or smiliar) while other tools do so (oXygen, Altova, xmlvalidation.com, etc.). Is there any explanation for this behaviour?
Thanks in advance
first thing which came into my mind - notepad++ does only coloring of xml,
Second thing, might it be that you use a 3rd party plugin like xml tools?
If so, you need to address your concerns to the respective author.
correct, I use the XML Tools plug-in. Will check this issue with the plug-in authors.