innerText in an XML file

[jacek]

if I'd like insert into a node as text the char '<' ?

You can't insert '<' into an XML document just like that, because it has special meaning --- it's a sign for a parser that a tag starts. That's why there are character entities in XML. For a parser &lt; is exactly the same thing as character < (of course this means that you can't use & in XML documents and you have to use &amp; instead).