Powered logic

In previous versions of nodeXML it was only possible to use queries with a WHERE branch of the form

$$e_1=v_1 \land e_2=v_2 \land \ldots \land e_n=v_n$$

With nodeXML 3.x you can combine terms like $e_i=v_i$ using AND, OR, NOT and parenthesis. At the moment it is not possible to use other comparison operators but =.