Querying sexps a la XPath?

[Elena]

Hello,

I have to extract data from some nodes belonging an XML document. I've
found a way to navigate the document structure in the XML Parser
Examples page in EmacsWiki (http://www.emacswiki.org/emacs/
XmlParserExamples).

However, I've often heard that sexps offer similar functionality as
XML. How would then you query a sexps structure?  AFAIK, there is no
library implementing something like SXPath in Emacs Lisp.

Thanks.