All white space is preserved, and is significant in queries.
select xmlextract("/a[@atr=' this or that ' ]",
"<a atr=' this or that '><b> which or what
</b></a>")
-------------------------------------------------
<a atr=" this or that ">
<b> which or what </b></a>
select xmlextract("/a[b=' which or what ']",
"<a atr=' this or that '><b> which or what
</b></a>")
---------------------------------------------
<a atr=' this or that '>
<b> which or what </b></a>