docs: protected void initRelations(Element root, CmsXmlContentDefinition contentDefinition) throws CmsXmlException {
  
          Iterator<Element> i = CmsXmlGenericWrapper.elementIterator(root, APPINFO_RELATION);
          while (i.hasNext()) {
              // iterate all "checkrule" elements in the "checkrule" node
              Element element = i.next();
              String elementName = element.attributeValue(APPINFO_ATTR_ELEMENT);
              String invalidate = element.attributeValue(APPINFO_ATTR_INVALIDATE);
              if (invalidate != null) {
                  invalidate = invalidate.toUpperCase();
              }
              String type = element.attributeValue(APPINFO_ATTR_TYPE);
              if (type != null) {
                  type = type.toLowerCase();
              }
              if (elementName != null) {
                  // add a check rule for the element
                  addCheckRule(contentDefinition, elementName, invalidate, type);
              }
          }
      }