[Xsltforms-support] Binding to the absence of a node

[Chimezie O. <chi...@gm...>]

Hello, I'm trying to support a situation where a group of controls (or
a single control) appear only if another node in the same instance
document does not appear.  When I was using XForms extension for
Firefox in the past, I was able to do it this way:


                            <xforms:group ref="current()[not(AbsentElement)]">
                                <xforms:trigger>
                                    <xforms:label>Add Skilled response
section</xforms:label>
                                    .. action to add AbsentElement to context..
                                </xforms:trigger>
                            </xforms:group>

The general idea is to only show a trigger if AbsentElement is not a
child of the current context, which will add that element if clicked.
However, I get the following exception

XSLTForms Exception
--------------------------

Error parsing the following XPath expression :

current()[not(AbsentElement)]

Unknown operator at '[not(AbsentElement)]' in 'current()[not(AbsentElement)]'

Can this be done in XSLTForms?

Thanks.

-- Chime