Drools Complex Rule Advice on Accumulating Facts

Question

I need some advice on how to write a rule for the following case. First, here are my facts:

SessionClock($now : new Date(getCurrentTime()))

ClickEvent( $userId : userId, $productId : productId, $event : "FAVORITE" / "REMOVE_FAVORITE" )

Product($id : id, $endDate : endDate)

Purchase ( $userId : userId, $purchasedProducts : purchasedProducts )

where purchasedProducts is a List of:

PurchasedProduct( $id : id, $price : price)

Now I would like to send a notification everytime at a particular hour:

Today is the endDate of a product and
User has favorited but hasn't unfavorited the product (from ClickEvent) and
User hasn't bought the product (from Purchase) and
Include all such products in one notification (basically I need to collect products)

I appreciate any help on this.

Thanks in advance!

That's all a bit hazy. What is the format of the endDate, e.g., is it a Date with h:m:s=0:0:0, i.e. midnight? Are these ClickEvent facts kept since the beginning of Time? Do you want this per user or over all users? — laune, Mar 13 '17 at 15:14
@laune `endDate` is a Java `Date` object, doesn't have to necessarily be midnight. `ClickEvent`s don't expire, at least not before `Product`s does. I am trying to achieve this per user. — Hasan Can Saral, Mar 13 '17 at 15:56
I've proposed a solution "per user". The logic for determining the expiry date can/should be hidden in a function. — laune, Mar 13 '17 at 16:21

laune · Accepted Answer · 2017-03-13T16:19:08.973

1

It may be a good idea to do this in steps

rule "interesting user/product"
when
  SessionClock( $now: time )
  Purchase( $uid: userId, $purchases: purchasedProducts )
  ClickEvent( userId == $uid, $pid: productId,
              event == "FAVORITE" )
  not ClickEvent( userId == $uid, productId == $pid,
                  event == "REMOVE_FAVORITE" )     
  Product( id == $pid, $endDate: endDate )
  eval( endDateIsToday( $now, $endDate ) )
then
end

rule "make Collection" extends "interesting user/product"
when
  not Collection( userId == $uid )
then
  insert( new Collection( $uid ) )
end

rule "fill Collection" extends "interesting user/product"
when
  $coll: Collection( userId == $uid, products not contains $pid )
then
  modify( $coll ){ addProduct( $pid ) }
end

A third rule, running with reduced salience, can do the notification.

Edit To clarify, endDateIsToday is a (DRL) function or static method. Collection is a class you need to define with a couple of fields: userId and set of product ids.

edited Mar 13 '17 at 16:19

answered Mar 13 '17 at 16:01

laune

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Are `endDateIsToday` and `addProduct` methods I should implement? – Hasan Can Saral Mar 13 '17 at 16:12
I've added a clarification. – laune Mar 13 '17 at 16:19
I see. Is there any way I can achieve this with `collect`/`accumulate` instead of creating a new class `Collection`? – Hasan Can Saral Mar 13 '17 at 16:29
In the same way, without `endDateIsToday` method if it's not a must, but a "can/should"? – Hasan Can Saral Mar 13 '17 at 16:31
The requirements aren't for me to define. Omit the eval if you need to find any product, no matter when it expires. – laune Mar 13 '17 at 16:34
Sorry, that's not what I meant. I want to achieve the same functionality without a drl function. However without creating any new Java classes is more important (i.e. `Collection`) – Hasan Can Saral Mar 13 '17 at 16:37
Hmm, thinking a little more, if it is going to be per user, I need a new Java class. Or I can get a global collection of `$pid`s, am I right? – Hasan Can Saral Mar 13 '17 at 16:55
I don't see how we assure that user has not purchased that product (relation to `$purchases` or `purchasedProducts`) – Hasan Can Saral Mar 14 '17 at 08:53
Right, but adding the constraint that the product is `this not memberOf $purchases` shouldn't be a problem. – laune Mar 14 '17 at 16:33
`$purchases` is not a list of `Product`s but a list of `PurchasedProduct`s. So I implemented `hashCode` and `equals` methods for both, and `eval ( $purchases not contains $pid )` works. Is this right? – Hasan Can Saral Mar 14 '17 at 19:36

Drools Complex Rule Advice on Accumulating Facts

1 Answers1