code: public CompatibilityMap getCompatibility(JSchema access) throws JMFSchemaViolationException {
      CompatibilityMap ans = null;
      if (compMaps == null)
        compMaps = new HashedArray(COMP_MAP_BUCKETS, 2);
      else
        ans = (CompatibilityMap)compMaps.get(access.getID());
      if (ans != null)
        return ans;
      ans = new CompatibilityMap(access, this);
      compMaps.set(ans);
      return ans;
    }
docs: Find the CompatibilityMap from a given access JSchema to this JSchema
  
  @param access the JSchema that is intended to be used as the access schema
  @return the desired CompatibilityMap if the schemas are compatible.  This method
  never returns null.
  @exception SchemaViolationException if the the JSchemas are not compatible