String () { String rootElementName = getElementName(); if (rootElementName == null || rootElementName.isEmpty()) { return XmlBundle.message("schema2.instance.no.valid.root.element.name.validation.error"); } final PsiFile psiFile = findFile(getUrl().getText()); if (psiFile instanceof XmlFile) { final XmlTag tag = getRootTag(psiFile); if (tag != null) { final XmlElementDescriptor descriptor = Xsd2InstanceUtils.getDescriptor(tag, rootElementName); if (descriptor == null) { return XmlBundle.message("schema2.instance.no.valid.root.element.name.validation.error"); } } } final String fileName = getOutputFileName(); if (fileName == null || fileName.isEmpty()) { return XmlBundle.message("schema2.instance.output.file.name.is.empty.validation.problem"); } return null; }