Re: [rules-users] Check for overlapping dates
It all depends on how many simultaneous instances you have in your
working memory. If you have just a few instances, a simple and single rule
can handle your case... you don't need to check for nulls, unless you want
to explicitly handle them:
rule "Overlapping Dates"
when
$a : Address ( )
$b : Address ( this != $a, beginDate > $a.beginDate, beginDate <
$a.endDate )
then
// $a and $b overlap
end
Now, I had to do the same thing for a system that handled telecom calls
and we had hundreds of thousands of call objects at once in the working
memory. As you may be aware, rules like the one above have the potential to
generate combinatorial explosions. In my case, I created a high performance
data structure to index the dates and detect the overlaps and used the rules
only to drive the execution (of course, there were hundreds of other rules
doing other things too). This way I avoided the combinatorial explosion.
Hope it helps.
Edson
2007/8/29, Brian Enderle <brianke(a)gmail.com>:
I have a situation where I need to check for overlapping dates in a
collection
of previous addresses. I am only performing this check after checking
that
the beginDate and endDate are not null.
Currently I am using an eval to perform an outside method. Does anyone
know
if and how I could perform this same check using Drools.
Curently my rules look something like this
gloabl java.lang.Boolean dateErrorExists; // starts off as false
global ValidationUtils utils;
rule "beginDate must exist"
when
Address ( beginDate != null )
then
dateMissing = true;
<display error>
end
rule "endDate must exist"
when
Address ( endDate != null )
then
dateMissing = true;
<display error>
end
rule "Previous Address dates cannot overlap"
salience -10
when
eval (dateMissing)
eval (utils.doAddressDatesOverlap())
then
<display error>
end
Our system simply runs thru the data checking the rules (no facts are
changed)
so the dateMissing global is reset to false everytime we perform our
validation.
The downside to this is I am having to re-get the data from the DB within
the
doAddressDatesOverlap() function. This function orders the Address
objects by
their startDates and then compares the endDate of one with the startDate
of
the next and returns false if they overlap.
If anyone knows of a cleaner, simpler or better way to perform this check
within Drools I would appreciate the input.
Thanks in advance,
Brian Enderle
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Edson Tirelli
Software Engineer - JBoss Rules Core Developer
Office: +55 11 3529-6000
Mobile: +55 11 9287-5646
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