[rules-users] depicting array in rules

[Swindells, Thomas]

Generally the advice when using drools is that if you are wanting to use an array (or other type of collection) then you should probably be normalising your data and putting the values of the collection into the working memory as their own object (pretend that drools is a relational database and follow the same rules as you would defining database tables and rows).  Sometimes you can't do this because of constraints on the environment you are work within but in your case you I think you have two options:

Each room conceptually has its own sprinkler therefore each Sprinkler object contains a single room field.
If a Sprinkler has the concept of operating over multiple rooms then have a Sprinkler object containing its ID and status, then have multiple SprinklerHeadLocation objects containing a reference to the Sprinkler and a single room each.


Rule " if fire in room start sprinkler if room has sprinkler"

No-loop true

when



      Fire($room : room)

      SprinklerHeadLocation(room == $room, $sprinklerId : sprinklerId)

      $sprinkler : Sprinkler(sprinklerId == $sprinklerId, status == false)??

      then

            modify($sprinkler){

                  setStatus(true)

                  };

End

Thomas

From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Esteban Aliverti
Sent: 09 June 2010 20:28
To: Rules Users List
Subject: Re: [rules-users] depicting array in rules

One way could be:

when

      Fire($room : room)
      $sprinkler : Sprinkler(room contains $room)
      Room (this == $room, someField == "SomeValue")
      then
            modify($sprinkler){
                  setStatus(true)
                  };
End

If you dont have the Room as a Fact Type, then:

when

      Fire($room : room)
      $sprinkler : Sprinkler(room contains $room)
      Room (someField == "SomeValue")from $room
      then
            modify($sprinkler){
                  setStatus(true)
                  };
End

I'm not 100% sure about this, but at least you can start from here

Best
2010/6/9 Fnu Mahalakshmi <FMahalakshmi at nyx.com<mailto:FMahalakshmi at nyx.com>>
Hi,

Is there any way I can represent an array of values in my rules??
I want to do this:
Fire{
Room,
Status}
Sprinkler{
Object [] Room = new Room[]{new Room(),new room()}
Status
}
Room{
Name,
Number}

Rule " if fire in room start sprinkler if room has sprinkler"
No-loop true
when

      Fire($room : room)
      $sprinkler : Sprinkler( room == $room) # how can I search through the array of room values here???????
      then
            modify($sprinkler){
                  setStatus(true)
                  };
End


Any Idea if that is possible to implement in rules???
I could do it with adding different instances of sprinkler and rooms. But I want to minimize the amount of repetition in data stored and loaded into the working memory.

Any idea??
Thank you,
M
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