[rules-users] AGE problem

[Wolfgang Laun]

For representing times, there are two distinct data types:
- absolute time, as a sequence of points on a timeline (the real "Time");
- durations, which are differences between points on a timeline.

Absolute time can be represented in a number of ways:
- as seconds (or milliseconds or nanoseconds), with 0 being some agreed-upon
point in Time,
- by Y,M,D,h,m,s according to some calendar;
- as Julian Days, in fractions.
It's obvious that calculations of any kind are best done with one of the
single-valued representations.

Durations can be expressed in any convenient unit, as long as there is a
well-defined conversion between the units with which you represent absolute
time and the units you desire to express durations.
There is no such well-defined conversion for (months and) years, and
therefore the idea to express a duration (precisely) in years is not used
commonly. (Astronomers settle for a year being equal to 365.25 Julian days;
so if this suits you, go ahead and base your calculations on that.)

For efficiency in rules, you might consider using Date.getTime() (or
Calendar.getTimeInMillis()) to obtain a point on the timeline, and to
express your notion of a year's duration (whatever it is) in the suitable
unit, and to use this for comparisons.

-W

On Thu, Feb 18, 2010 at 1:43 PM, Pavel Tavoda <pavel.tavoda at gmail.com>wrote:

> Hello,
> I would like to calculate AGE of object based on Date inside object, I
> can use eval but I hope it's so basic functionality that Drools should
> have it. It's also performance problem if I need to use EVAL in many
> rules (let's say 100 in XLS). I'm playing with some FUSION features
> like:
>     $now : Now() && $order : SecurityOrder(this before[400d, 0d] $now)
> should work but I can't specify YEARS as constant. That's a problem
> for long time because 30*365d isn't same as 30 years if you consider
> leap years. Is it possible some easy way to calculate AGE of something
> with correct time handling and compare to years? Something like:
>    SecurityOrder( age(createdDate) > 20y, age(createdDate) < 25y)
> or by FUSION:
>     $now : Now() && $order : SecurityOrder(this before[25y, 20y] $now)
>
> For now I'm using following function in eval() but it's becoming
> performance problem:
> function boolean between(Calendar currentDate, Date oldDate, int from, int
> to) {
>        Calendar fromCal = Calendar.getInstance();
>        fromCal.setTime(oldDate);
>        fromCal.add(Calendar.YEAR, from);
>
>        Calendar toCal = Calendar.getInstance();
>        toCal.setTime(oldDate);
>        toCal.add(Calendar.YEAR, to);
>        return currentDate.after(fromCal) && currentDate.before(toCal);
> }
>
> Thank you
>
> Pavel
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20100222/4b7ce511/attachment.html