[jboss-jira] [JBoss JIRA] (DROOLS-24) forall( p1 p2 p3...) --> not forall

[Davide Sottara (JIRA)]

    [ https://issues.jboss.org/browse/DROOLS-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12802586#comment-12802586 ] 

Davide Sottara commented on DROOLS-24:
--------------------------------------

Remember the semantics of "not" and "forall" in Drools. The former is actually "not exists", while

forall( $x:A() B($x) C($x) )

reads as "for all $x such that A($x), there exists $b,$c : $b : B($x) and $c : C($x)"
which, by deMorgan, is equivalent to : "there is no $x such that, at the same time, A($x) and neither exists $b:B($x) nor exists $c:C($x)".

in DRL-like : not( $x:A() and not( B($x) and C($x) ) ) --> not( $x:A() and ( not B($x) or not C($x) ) )

So, while a bit cryptic, I think that the documentation is correct. 
One might argue whether FOL is captured appropriately or not, but that's a different question

                
> forall( p1 p2 p3...) --> not forall
> -----------------------------------
>
>                 Key: DROOLS-24
>                 URL: https://issues.jboss.org/browse/DROOLS-24
>             Project: Drools
>          Issue Type: Task
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 5.5.0.Final
>         Environment: all
>            Reporter: Marc Dzaebel
>            Assignee: Mark Proctor
>            Priority: Trivial
>              Labels: documentation
>
> Expert guide: 
> "As a side note, forall( p1 p2 p3...) is equivalent to writing:
>  not(p1 and not(and p2 p3...))"
> --> insert not
> "As a side note, not forall ..."

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