[rules-users] Getting Started with an simple sample

[Wolfgang Laun]

Keeping track of external entities in Working Memory is possible but
you'll have to provide a safe restart mechanism.

Let's say you have events Reading( String detName, int value) and
Marker( String detName ), your rules would be

rule "above threshold"
when
   Reading( $d: detName, $v: value > 5 )
   not Marker( detName == $d )
then
   // create file
   insert new Marker( $d );
end

To be restart-safe, provide Java code checking for the existence of
files and insert Marker files accordingly.

-W

On 26/04/2013, Stefan Schuster <stefan.m.schuster at gmail.com> wrote:
> Hi Bojan,
>
> thanks a lot for your fast response.
>
> but how can I guarantee that there is only one textfile per detector
> created, even if the detecor has a value above 5 for a longer time?
> Obviously the method for textfile-creation could check if there already
> exists a file on the filesystem, but that doesn't feel "drools-like" to me.
>
> further ideas?
>
> thanks
> Stefan
>
>
> 2013/4/26 Bojan Janisch <bojan.janisch at scai.fraunhofer.de>
>
>> Hi Stefan,
>>
>> after you know what in the knowledgesession shall be, you have to think
>> how you could check the value that the detectors return. For this you
>> could
>> create a new class e.g. MeasureResult which contains the result of the
>> detectors. So instead of inserting the value, you insert the object (that
>> contains the value) into the session. Now your rule only have to check if
>> there is a MeasureResult object and depending on the value, do something.
>>
>> For example:
>>
>> rule "Measure >= 5"
>> when
>>     MeasureResult(result >= 5)
>> then
>>     //insert textfile creation here
>> end
>>
>> rule "Measure <= 3"
>> when
>>     MeasureResult(result <= 3)
>> then
>>     //insert textfile deletion here
>> end
>>
>> Of course for these rules your MeasureResult class need a variable called
>> result and getter-Methods for it.
>>
>> Greetings
>> Bojan
>>
>>
>>
>> ----- Ursprüngliche Mail -----
>> Von: "Stefan Schuster" <stefan.m.schuster at gmail.com>
>> An: "Rules Users List" <rules-users at lists.jboss.org>
>> Gesendet: Freitag, 26. April 2013 11:30:40
>> Betreff: [rules-users] Getting Started with an simple sample
>>
>>
>>
>>
>>
>> Hello,
>>
>> I’m still in the phase of learning the basics with drools. Therefor I
>> created a simplified problem that I try to realize it with drools:
>>
>> I have several detectors, each of them measures something and converts it
>> into an integer value between 1 one 6. Every Minute a new measurement is
>> performed.
>>
>> When a detector reaches a value of 5 or above, a textfile is created with
>> the name of the detector as filename and a predefined text as content.
>> When
>> the detector reaches a value of 3 or less, the texfile is deleted.
>>
>> My problem is that I’m still “thinking in java” and not yet “thinking in
>> drools”.
>>
>> I guess the measured values would be facts that I insert (like the
>> key-pressed events in the pong-example) to the knowledgebase. But now I
>> stumble, I have no idea how to continue. Could anyone give me a helping
>> hand for the next steps?
>>
>> Thanks in advance
>>
>> Stefan
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