How to create a score from several drools decision tables?

问题

I'm new to drools and trying to use guvnor to build a simple Framingham score calculator.

An example is: lets say you are a 30yo male, you start with -9 points. If your total cholesterol is 180, add 4 points, if your a smoker add 8 points, if your HDL cholesterol is over 60, subtract 1 point, and if your blood pressure is 135 then add 1 point. Giving you a result of +3.

The tables on the score sheet seem like a great scenario for a drools decision table(s).

I'm having trouble figuring out how to add the individual score numbers together.
I stared by creating a new "FraminghamScore" fact for my result column, but then I need to add these facts together.

I tried to join all the tables into 1, but that gets complex and redundant real quick.

It looks like if I were to create my FraminghamScore in java, I could have a incrementValue(int) method that I could call, but then I couldn't figure out how to pass a number to it.

回答1:

In case you decide to refactor your app to use drools instead, and if someone else is looking for a solution to a similar problem, here are my two cents of drools knowledge.

Your facts could be something like this

// Fact for the scoring
class FraminghamScore {
  private int total;

  public void increment( int value ) { total += value; }
  public int getTotal() { return total; }
}

// Fact for the subject
class Person {
  public enum Gender{ MALE, FEMALE };
  private Gender gender;
  private int age;
  private int cholesterol;
  private boolean smoker;
  // Rest of the fields + getter/setters as needed
}

Your decision tables would be something like below. As I see it, there will be some duplication in age checking for example, I can't think of a way to get rid off those.

Condition                    | Condition                    |  Action
-----------------------------------------------------------------------------------
                      $p : Person()                         |
                      $s : FraminghamScore()                |
-----------------------------------------------------------------------------------
p.gender                     | $param                       |  s.increment($param);
                             |                              |  update(s);
-----------------------------------------------------------------------------------
MALE                         | p.age >= 20 && p.age <= 34   |  -9
MALE                         | p.age >= 35 && p.age <= 39   |  -5
-- Rest of the age groups + same for females


Condition                    | Condition          |  Action
-----------------------------------------------------------------------------------
                      $p : Person()               |
                      $s : FraminghamScore()      |
-----------------------------------------------------------------------------------
p.gender                     | p.smoker           |  s.increment($param);
                             |                    |  update(s);
-----------------------------------------------------------------------------------
MALE                         | true               |  -9
MALE                         | false              |  -5

And so forth.

Now looking at the tables, I see that there will be awfully lot of duplication with the age checking. Can't think of a better way at the moment, though. Hope this helps at least a bit.

EDIT

You can have the FraminhamScore fact only to hold the amount of point per each rule instead of summing them together there. With this option, you'd add a score fact to working memory per rule and use query to fetch them in the end and then do math. This might keep your decision tables cleaner.

来源：https://stackoverflow.com/questions/13096040/how-to-create-a-score-from-several-drools-decision-tables

标签

drools