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Using Natural Language Expressions Inside OpenRules Tables

This document will explain how rules could be expressed in plain English in OpenRules decision tables.  The concrete examples will be shown to demonstrate the use of natural language expressions to define different rules.  We will take a relatively complex decision table and will show how to use predefined OpenRules types such as FromToInt, CompareInt, and DomainString to simplify this table for a business user.  While simplicity is always a matter of taste, the actual objective is to demonstrate the use of natural language inside OpenRules tables.

Basic Example

Using FROM-TO Intervals

Comparing Integer and Real Numbers

Representing String Domains

Representing Domains of Numbers

Using Java Expressions

Expanding and Customizing Predefined Types

Performance Considerations

Basic Example  ►top

We will use a decision table "DebtResearchRules" from the sample rule project "Loan1" included into the standard OpenRules installation.  Here is the default representation of the debt research rules:

Rules void DebtResearchRules(LoanRequest loan, Customer c)
C1 C2 C3 C4 C5 C6 C7 A1
c.mortgageHolder.equals(YN) c.outsideCreditScore>min &&
c.outsideCreditScore<=max		 c.loanHolder.equals(YN) op.compare(c.creditCardBalance,value) op.compare(c.educationLoanBalance,value) contains(rates,c.internalCreditRating) c.internalAnalystOpinion.equals(level) loan.debtResearchResult = level;
out("Debt Research Result:"+level);
String YN int min int max String YN Operator op int value Operator op int value String[] rates String level String level
IF
Mortgage Holder		 AND
Outside Credit Score		 AND
Loan Holder		 AND
Credit Card Balance		 AND
Education Loan Balance		 AND
Internal Credit Rating		 AND
Internal Analyst Opinion		 THEN
Debt Research Recommendations
Min Max Oper Value Oper Value
Yes                           High
No 100 550                       High
No 550 900 Yes <= 0                 Mid
No 550 900 Yes > 0 > 0             High
No 550 900 Yes > 0 <= 0 A B C       High
No 550 900 Yes > 0 <= 0 D F         Mid
No 550 900 No > 0                 Low
No 550 900 No <= 0 <= 0             Low
No 550 900 No <= 0 > 0 D F         High
No 550 900 No <= 0 > 0 A B C       Low
                          High High
                          Mid Mid
                          Low Low
                             

We are going to modify conditions C2, C4, C5, and C6 by using different OpenRules representation options.

Using FROM-TO Intervals  ►top

The condition C2 above represents the fact that customers's outside credit score should be between min and max. To be exact, the condition is presented as the following Java snippet:

    c.outsideCreditScore>min && c.outsideCreditScore<=max

where min and max are parameters defined in two different sub-columns of the column C2.  Note that the comparison logic is hard-coded inside implementation: c.outsideCreditScore is strictly greater than min and less than or equals to max. We may easily switch to only one column and allow a business user him/herself to define the comparison logic for each particular rule using any reasonable representation of an interval min-max.  Here is an example of the properly modified condition C2:

C2
interval.contains(c.outsideCreditScore)
FromToInt interval
AND
Outside Credit Score