title: multiple discriminator columns for persistent subclasses
body: <p>I have banged my self with a very particular problem. Using OpenJPA (KODO 4.1) is there a way to use more than one column as a discriminator column?</p>
  
  <p>My problem is that i have a table structure (which i have limited ability to modify of course) similar to this:</p>
  
  <pre><code>Table  VEHICLE      EXPENSIVE_CAR  CHEAP_CAR       EXPENSIVE_BOAT    CHEAP_BOAT
  ---------------------------------------------------------------------------------
         HORSE_POWER  LUXURY_ACC     CLASIFICATION   SIZE              SIZE
         MEDIUM       EXTRAS                         TV_SIZE
         IS_EXPENSIVE CLASIFICATION
  </code></pre>
  
  <p>Where medium would discriminate between boat and car and is expensive would discriminate bettwen expensive or cheap.</p>
  
  <p>So, is there any way to achieve this with the inheritance capabilities provided by OpenJPA (i know hibernate can use discriminator formulas but i am trying not to switch from the default JPA provider).</p>
  
  <p>As a bonus if you can tell me about the custom <a href="http://openjpa.apache.org/builds/1.0.2/apache-openjpa-1.0.2/docs/manual/jpa_overview_mapping_discrim.html" rel="nofollow noreferrer">discriminator strategies</a> from OpenJPA that would be great since i have a hunch that it could be a plausible solution (even though i would prefer a vendor independent one)</p>
  
  <p>Thanks a lot</p>