Rather than comparing line-by-line, DITA Merge identifies and matches up all the elements across your DITA documents, so it has a meaningful and dependable basis for comparing and merging. This pairing process uses a combination of element names, parent names, position in the XML tree and the structure of child elements.
DITA Merge outputs well-formed, valid DITA files so the resulting output is compatible with your existing DITA tools. DITA Merge has been designed to make the document merge process consistent and straightforward.