[rules-users] To accumulate or not to accumulate

[Wolfgang Laun]

There are some details that one should consider before deciding on a
particular implementation technique.

   - Are all Sentences contiguous, i.e., s1.end = pred( s2.start )
   - Can a ManualAnnotation start on one Sentence and end in the next or any
   further successor?

As in all problems where constraints depend on an order between facts,
performance is going to be a problem with increasing numbers of Sentences
and ManualAnnotations.

Your accumulate plan could be a very inefficient approach. Creating O(N*N)
pairs and then looking for an overlapping window is much worse than looking
at each window, for instance. But it depends on the expected numbers for
both.

-W



2011/8/19 Bruno Freudensprung <bruno.freudensprung at temis.com>

> **
> Hello,
>
> I am trying to implement rules handling "Sentence", "ManualAnnotation"
> objects (imagine someone highligthing words of the document). Basically
> "Sentence" objects have "start" and "end" positions (fields) into the text
> of a document, and they are Comparable according to their location into the
> document.
>
> I need to write rules using the notion "window of consecutive sentences".
>
> Basically I am not very interested by those "SentenceWindow" objects, I
> just need them to define a kind of proximity between "ManualAnnotation"
> objects.
> What I eventually need in the "when" of my rule is something like:
>
> when
>     ... maybe something creating the windows
>     a1 : ManualAnnotation ()
>     a2 : ManualAnnotation (this != a1)
>     SentenceWindow (this includes a1, this includes a2)
> then
>     ... do something with a1 and a2 since they are "close" to each other
> end
>
> As I don't know the "internals" of Drools, I would like to have your
> opinion about what the best "idiom":
>
>    - create all SentenceWindow objects and insert them in the working
>    memory, then write rules against all the facts (SentenceWindow and
>    ManualAnnotation)
>     - implement an accumulator that will create a list of  SentenceWindow
>    object
>
>
> The first option could look like:
>
> rule "Create sentence windows"
>    when
>       # find 3 consecutive sentences
>       s1 : Sentence()
>       s2 : Sentence(this > s1)
>       s3 : Sentence(this > s2)
>       not Sentence(this != s2 && > s1 && < s3)
>    then
>       SentenceWindow swindow = new SentenceWindow();
>       swindow.setStart(s1.getStart());
>       swindow.setTheend(s3.getEnd());
>       insert(swindow);
> end
>
> ... Then use the first rule "as is".
>
> The accumulator option could look like (I am not really sure the syntax is
> correct) :
>
> when
>     *$result : ArrayList() from accumulate ( $s: Sentence(),
> buildwindows($s))*
>     a1 : ManualAnnotation ()
>     a2 : ManualAnnotation (this != a1)
>    * SentenceWindows (this includes a1, this includes a2) **from $result*
>  then
>     ... do something with a1 and a2 since they are "close" to each other
>  end
>
> Is it possible to decide if one way is best than the other?
>
> And one last question: it is possible to "parametrize" an accumulator (in
> order to provide the number of sentences that should be put in the windows)?
> I mean something like:
>
> when
>     $result : ArrayList() from accumulate ( $s: Sentence(), *
> buildwindows(3,* $s))
>
>
> Thanks in advance for you insights,
>
> Best regards,
>
> Bruno.
>
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