void startExternalEntity(String name, String systemId, boolean stackOnly)
            throws SAXException {
        // The following warning was deleted because the application has the
        // option of not setting systemId. Sun's JAXP or Xerces seems to
        // ignore this case.
        /*
         * if (systemId == null) warn ("URI was not reported to parser for
         * entity " + name);
         */
        if (!stackOnly) // spliced [dtd] needs startEntity
        {
            lexicalHandler.startEntity(name);
        }
        entityStack.push(systemId);
    }
<b>SAX2</b>: Assigns the specified property. Like SAX1 handlers, these
may be changed at any time.
src/nu/validator/gnu/xml/aelfred2/SAXDriver.java