title: How to Override rules and decision tables in Drools 6?
body: <p>There is a scenario where we have set of master rules. One of the rules is similar to below rule:</p>
  
  <pre><code>rule "Check Eligibility"
  when 
      $response(type=="rest",age== 25)
  then 
     $response.setSendLetter("Y");
     $response.setUpdateStatus("eligible");
  end
  </code></pre>
  
  <p>These rules will be available to customers. We want our customers to be able to customise the rule. If decide not to customise, then rule should apply for them. Customising could be adding additional conditions in "when" or could be overriding the existing conditions and also adding or modify the "when" part. They can also add to "then" part of the rule.</p>
  
  <p>Something like:</p>
  
  <pre><code>rule "Check Eligibility"
  when 
     $response(type=="rest",age== 27, state="IL")
  then 
     $response.setSendLetter("N");
     $response.setUpdateStatus("eligible");
     $response.setSendEmail("Y");
  end
  </code></pre>
  
  <p>We also have some decision tables which need similar customisation.</p>
  
  <p>From rules there was initial suggestion to use "extends" but from what I know "extends" works as "AND" where it will check conditions on both parent and child and if both are true it will do "then" part. </p>
  
  <p>The possible solution I could think off is to clone the master repository for each customer and then whenever there is change in master repository rule, we do a pull onto the customer repositories. The possible issue could be occasional merge conflicts that may have to be resolved manually. </p>
  
  <p>The clone solution hasn't been accepted in the team, so wanted to know what are possible solutions to achieve "override" for both rules and decision tables?</p>