[rules-users] How can I write a rule that will only fire once for every object in the working memory

[Mark Proctor]

You can write your own agenda-filter to keep track of which objects have 
fired for which rules and cancel the activation if it's fired before. 
You may also have some luck with lock-on-active.

Mark
Waruzjan Shahbazian wrote:
> Hallo,
>
> I was wondering if it's possible to create a rule that can only be 
> activated once. So if at a certain point the LHS is matching, it will 
> be fired and deactivated immediately, so the rule never ever gets 
> fired for the object it has updated, no matter if the LHS will matches 
> after a few updates()'s at a later time.
>
> The only way I can achieve this, is by manually evaluating in the LHS 
> if the certain object has the certain values I am gonna set in the 
> RHS, so if it has, I don't fire the rule. But this takes some 
> unnessery time and I was wondering if it couldn't be more easier/faster.
>
> Example:
> ----------------------------------------------------
>
> $product : Product(title matches "(?i).*SOMEWORD.*", $productClasses : 
> productClasses)
> $activated : Boolean(booleanValue == false)
>                        from accumulate($productClass : ProductClass( 
> schema.code == "DROOLS", code == "012345" ) from $productClasses,
>                                  init(boolean activated = false;),
>                                  action( activated = true;),
>                                  result( activated ) )
>
> then
>
> Set the schema and code of the product
>
> update($product)
>
> ----------------------------------------------------
>
> So in the example above I am actually iterating over all the 
> productClasses of the product and checking if they have the right 
> codes. If I actually could just fire the rule on all the products
> whose title matches "(?i).*SOMEWORD.*", and deactivate the rule for 
> the instance of the $product, I wouldn't have to accumulate over the 
> list of productClasses of the product to see if the rule
> was fired before for this particulare product.
>
> The "no-loop" attribute doesn't work here, because it gets ignored 
> when another rule updates the product. So when this rule has fired, 
> and updated the product, some other rule gets activated and updates 
> the product, and than this rule gets fired, because the LHS still 
> matches.
>
> Any help is welcome,
>
> Waruzjan
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