[rules-users] Using Drools Fusion to compute overlaps of many intervals

[Raphael Jolivet]

Thanks .
This completely answers my questions.

Raphael


2013/8/15 Wolfgang Laun <wolfgang.laun at gmail.com>

> See inline.
>
> On 14/08/2013, Raphael Jolivet <raphael.jolivet at gmail.com> wrote:
> > Hi Drools guys.
> >
> > I just asked the following question on
> > StackOverlow<
> http://stackoverflow.com/questions/18219841/using-drools-fusion-to-compute-overlaps-of-many-intervals
> >
> > .
> > Could you please help :
> >
> > I am already using Drools to do some *preprocessing of an allocation
> > problem
> > * (resources vs operations). The operations are already time *intervals*
> > but
> > I did not need to leverage the Drools Fusion features yet.
> >
> > There is a new requirement for having some *attributes of my resources
> > changing over time*.
> >
> > I am willing to model this (the change of values over time) as *"events"
> in
> > Drools* and take advantage of Drools Fusion, in *Cloud* mode.
> >
> > Hence I will have to match those "dynamic" attributes events against my
> > operations (again declared as events in Drools fusion). This will require
> > Drools to *compute a great amount of intervals overlaps*.
> >
> > I have several questions :
> >
> >    - I have found the *overlap* operator to be kind of counter-intuitive,
> >    and to not actually process*overlap* as we usually describe it.
>
> The definition of temporal operators in Drools follows
> well-established research. The intent is to be able to pinpoint very
> specific relations, with more general or symmetric relations requiring
> disjunctions.
>
> > I would
> >    expect [a;b] and [c;d] to overlap if *(b > c) and (a < c)*. Is there a
> >    time operator for that ?
>
> There are only those described in the Fusion manual.
>
> > Or should I use a composition of several time
> >    operators ?
>
> Basically: yes, but see below.
>
> >    - Does Drools Fusion uses any kind of internal optimization for this
> >    kind of problem ?
>
> Not anything beyond the optimization provided by Rete (or whatever
> algorithm the Engine uses). You can look at the implementations of the
> operators: it's a pretty straightforward set of comparison, although
> the operator parameters add a level of complexity.
>
> You probably should implement your specific concept of "overlap" as a
> custom operator.
>
> > Naively matching N intervals against M intervals would
> >    require *0(N x M)* operations. I have found a way to go down to *(M x
> >    log(M) + N x log(N))*, by sorting the intervals beforehand : Should I
> >    prepare the pair of overlaps for Drools in advance ?
>
> You may have to design an approach that accumulates events as they
> occur, determining whether a new event is one that joins a set of
> overlapping events or not.
>
> >    - Related to the previous question : Is there any benefit in this case
> >    (in term of performances), of using *Drools Fusion* instead of
> *regular
> >    Drools* together with conditions over timestamps and duration ?
>
> Drools Fusion *is* what you call "regular Drools". It is just a
> marketing curlicue, to put a tag on a relatively small set of
> features: timestamp/duration, temporal ops, windows, cloud/stream, and
> event expiry. But there's only one Engine. Especially temporal
> operators is just syntactic sugar.
>
> -W
>
> >
> > Thanks for your advice
> > Brgds,
> >
> > -- Raphael
> >
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