[rules-users] Check for overlapping dates

[Brian Enderle]

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