Re: [rules-users] To accumulate or not to accumulate
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(a)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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