[rules-dev] Perhaps an undocumented feature of Backward Chaining?

[Wolfgang Laun]

Still not resolved...

On 22 June 2011 21:40, Mark Proctor <mproctor at codehaus.org> wrote:

> heh, I made a mistake with the rule
> ( Location(z, y;) and ?hasFood(x, z;) )
> should be
> ( Location(z, y;) and hasFood(x, z;) )
>
> Otherwise it's not reactive, and then ordering matters.
>
> With that change I can do the insertions in any order and all is fine.
>
>
This works for the example you gave. But the one taken from the
"Introduction" still depends on the order the facts are inserted. Below is
the .drl, which does not need any pojos. Rule kickOff contains the order
that produces nothing to see and eat:
You are in the table
  You can see []
  You can eat []

Insert Here after the others, and it works.

-W

 import java.util.List

declare Thing
    thing : String @key
end

declare Edible extends Thing
end

declare Location extends Thing
    location : String  @key
end

declare Here
    place : String
end

rule kickOff
when
then
    System.out.println( "insert Here" );
    insert( new Here( "table" ) );
    System.out.println( "insert Edible" );
    insert( new Edible( "peach" ) );
    System.out.println( "insert Location" );
    insert( new Location( "peach", "table" ) );
end

# 2011-06-22
query isContainedIn( String x, String y )
    Location(x, y;)
    or
    ( Location(z, y;) and /*?*/isContainedIn(x, z;) )
end

query whereFood( String x, String y )
    ( Location(x, y;) and
    Edible(x;) )
    or
    ( Location(z, y;) and /*?*/whereFood(x, z;) )
end

query look(String place, List things, List food)
    Here(place;)
    things := List() from accumulate( Location(thing, place;),
                                      collectList( thing ) )
    food := List() from accumulate( /*?*/whereFood(thing, place;),
                                    collectList( thing ) )
end

rule reactiveLook
when
    Here( $place : place)
    /*?*/look($place, $things; $food := food)
then
    System.out.println( "You are in the " + $place);
    System.out.println( "  You can see " + $things );
    System.out.println( "  You can eat " + $food );
end
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-dev/attachments/20110623/cc1ce2f3/attachment.html