Xpath or DOM?

In my thesis I will attempt to implement a program that can merge libraries of XML documents.
I can't seem to find any sort of good comparisson between Xpath and DOM. Anyone with experience that would like to shed some light into what might be a good option to build an algorithm around?

XPath is the means by which you query a DOM (typically loaded from XML, but this isn't a necessity). It's a "query language" allowing you to select one or more nodes from a DOM.

or if you want an analogy
SQL is the means by which you query a relational Database



You don't need to create a program to merge XML documents. XSLT is the technology that is catering to that (and many other) problems already. XSLT uses XPath to query the DOM and transform one document into another.