The function isnull() identifies whether the given argument, which may be of any type, is null.
isnull(argument)
The function takes arguments of any type.
Returns the Boolean value true when the argument is null, and otherwise returns the Boolean value false.
Dataset
XPDL-rule
Result
Jack
rule: r1
{
query: {phrase(lemma(noun), {optional(lemma(noun))}:surname)}:name
result: Name = $name
attribute: IsNull= isnull($surname)
}
yes
Jack Nicholson
no