[rules-users] How do I write a rule to detect a missing value in a group of facts?

[Wolfgang Laun]

2012/2/9 <GPatel at tsys.com>

> Beautiful!
>
> How would a business user (non-programmer) write such a rule.
>
There's some evidence that it's difficult to "un-think" your procedural
programming imprinting. A non-programmer might even have the edge over a
programmer.

But rule programming isn't a silver bullet - lots of stuff to learn.

The only way I can think of is create a dsl sentence for this specific
> condition
>
Even so.
-W


> ------------------------------
>
> *  From: *Wolfgang Laun [wolfgang.laun at gmail.com]
> *  Sent: *02/09/2012 05:02 PM CET
> *  To: *Rules Users List <rules-users at lists.jboss.org>
> *  Subject: *Re: [rules-users] How do I write a rule to detect a missing
> value in a group of facts?
>
> Don't think procedurally, just write the *rule* for a missing post ;-)
>
> rule "missing fence post"
> when
>     FencePost( $d: distanceFromStart )
>     FencePost( distanceFromStart == $d + 2*FencePost.GAP )
>     not FencePost( distanceFromStart == $d + FencePost.GAP )
> then
>     System.out.println( "Missing: " + ($d + FencePost.GAP) );
> end
>
> -W
>
> On 9 February 2012 16:41, mikeg <mike at thegoldners.com> wrote:
>
>> I need to write a rule to identify a missing element in a group of facts.
>>
>> For example, let us say I want to ensure that my fence has a fence post
>> every 8 feet.  My fact declaration is as follows:
>>
>> declare FencePost
>>  identifier : String
>>  distanceFromStart: Long
>> end
>>
>> If I add the following facts into my session:
>>
>> FencePost("a", 0)
>> FencePost("x", 8)
>> FencePost("e", 24)
>>
>> I want a rule that will notify the user that there is a missing fence post
>> between "x" and "e".
>>
>> I've been looking into using "collect" into a TreeSet/TreeMap to get a
>> collection sorted on the "distanceFromStart", but I cannot figure out how
>> to
>> compare adjacent elements in the collection.
>>
>> Any ideas?
>>
>> --
>> View this message in context:
>> http://drools.46999.n3.nabble.com/How-do-I-write-a-rule-to-detect-a-missing-value-in-a-group-of-facts-tp3729818p3729818.html
>> Sent from the Drools: User forum mailing list archive at Nabble.com.
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
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