code: public boolean release(DTM dtm, boolean shouldHardDelete)
    {
      // %REVIEW% If it's a DTM which may contain multiple Result Tree
      // Fragments, we can't discard it unless we know not only that it
      // is empty, but that the XPathContext itself is going away. So do
      // _not_ accept the request. (May want to do it as part of
      // reset(), though.)
      if(m_rtfdtm_stack!=null && m_rtfdtm_stack.contains(dtm))
      {
        return false;
      }
    	
      return m_dtmManager.release(dtm, shouldHardDelete);
    }
docs: Release a DTM either to a lru pool, or completely remove reference.
  DTMs without system IDs are always hard deleted.
  State: experimental.
  
  @param dtm The DTM to be released.
  @param shouldHardDelete True if the DTM should be removed no matter what.
  @return true if the DTM was removed, false if it was put back in a lru pool.