private void handleArc(final StartElement element) {
        String arcId = null;
        String source = null;
        String target = null;
        Iterator<?> attributes = element.getAttributes();
        while (attributes.hasNext()) {
            Attribute attr = (Attribute) attributes.next();
            if (attr.getName().toString().toLowerCase().equals("id")) {
                arcId = attr.getValue();
            } else if (attr.getName().toString().toLowerCase().equals("source")) {
                source = attr.getValue();
            } else if (attr.getName().toString().toLowerCase().equals("target")) {
                target = attr.getValue();
            }
        }
        if (arcId != null && source != null && target != null) {
            String arc_info[] = {arcId, source, target};
            arcs_info.add(arc_info);
        } else {
            System.err.println("Unvollständige Kante wurde verworfen!");
        }
        //Die id von Kanten wird nicht gebraucht
        lastId = null;
    }