The source_node of the domain accepts XPATHs that start with / and // only

[ymark]

We should be compliant with the standards
http://www.w3schools.com/xsl/xpath_syntax.asp

Can we support the following? :
/ Selects from the root node
// Selects nodes in the document from the current node that match the selection no matter where they are
. Selects the current node
.. Selects the parent of the current node
@ Selects attributes