One Person can be part of multiple Events and one Event can have multiple Persons.
In a specific Event page (let's say "Event A") I want a datagrid with Persons that are not listed to that Event yet.
The XPath constraint [not(MyFirstModule.Person_Event/MyFirstModule.Event)] is not suitable. The datagrid then will not show Persons that are part of another Event and are still eligible to join "Event A".
How should my XPath constraint look like, when I only want to see the Persons that are not associated to "Event A"?