code: public static boolean isValidSchematron (@Nullable final Source aSource)
    {
      if (aSource == null)
        return false;
  
      try
      {
        // Get a validator from the RNC schema.
        final Validator aValidator = RelaxNGCompactSchemaCache.getInstance ().getValidator (SCHEMATRON_RNC);
  
        // Ensure a collecting error handler is set
        final ErrorHandler aOldEH = aValidator.getErrorHandler ();
        CollectingSAXErrorHandler aCEH;
        if (aOldEH instanceof CollectingSAXErrorHandler)
          aCEH = (CollectingSAXErrorHandler) aOldEH;
        else
        {
          aCEH = new CollectingSAXErrorHandler ();
          aValidator.setErrorHandler (aCEH.andThen (aOldEH));
        }
  
        // Perform validation
        aValidator.validate (aSource, null);
  
        // Check results
        return aCEH.getErrorList ().getMostSevereErrorLevel ().isLT (EErrorLevel.ERROR);
      }
      catch (final SAXException ex)
      {
        // Document is not valid in respect to XML
      }
      catch (final IOException ex)
      {
        LOGGER.warn ("Failed to read source " + aSource, ex);
      }
      return false;
    }
docs: Check if the passed source is a valid schematron instance.
  
  @param aSource
  The source to check. May be <code>null</code>.
  @return <code>true</code> if the schematron is valid, <code>false</code>
  otherwise.