Edson Tirelli-3 wrote:
>
> Also, remember you can negate operators:
> Parent( collection contains $child )
> Parent( collection not contains $child )
> That is more efficient than composing "exists"/"not" and "from".
>

True, but "children not contains $child" expects to have the Child bound in
a previous condition, implying (to my understanding) that "a" child must be
present to match the condition, while this might not and, in my rule,
mustn't be the case at all.

Correct. The way to represent that scenario without using "from" is to write it like this:

not(

$child : Child( name == "bob" )

$parent : Parent( children contains $child )

)

Edson