public String[] knownNamespaces() {
   final PsiElement parentElement = getParent();
   BidirectionalMap<String, String> map = initNamespaceMaps(parentElement);
   Set<String> known = Collections.emptySet();
   if (map != null) {
     known = new HashSet<String>(map.values());
   }
   if (parentElement instanceof XmlTag) {
     if (known.isEmpty()) return ((XmlTag) parentElement).knownNamespaces();
     ContainerUtil.addAll(known, ((XmlTag) parentElement).knownNamespaces());
   } else {
     XmlExtension xmlExtension = XmlExtension.getExtensionByElement(this);
     if (xmlExtension != null) {
       final XmlFile xmlFile = xmlExtension.getContainingFile(this);
       if (xmlFile != null) {
         final XmlTag rootTag = xmlFile.getRootTag();
         if (rootTag != null && rootTag != this) {
           if (known.isEmpty()) return rootTag.knownNamespaces();
           ContainerUtil.addAll(known, rootTag.knownNamespaces());
         }
       }
     }
   }
   return ArrayUtil.toStringArray(known);
 }
 @Nullable
 @NonNls
 public String getSubTagText(@NonNls String qname) {
   final XmlTag tag = findFirstSubTag(qname);
   if (tag == null) return null;
   return tag.getValue().getText();
 }
  public XmlNSDescriptor getNSDescriptor(final String namespace, boolean strict) {
    final XmlTag parentTag = getParentTag();

    if (parentTag == null && namespace.equals(XmlUtil.XHTML_URI)) {
      final XmlNSDescriptor descriptor = getDtdDescriptor(XmlUtil.getContainingFile(this));
      if (descriptor != null) {
        return descriptor;
      }
    }

    Map<String, CachedValue<XmlNSDescriptor>> map = initNSDescriptorsMap();
    final CachedValue<XmlNSDescriptor> descriptor = map.get(namespace);
    if (descriptor != null) {
      final XmlNSDescriptor value = descriptor.getValue();
      if (value != null) {
        return value;
      }
    }

    if (parentTag == null) {
      final XmlDocument parentOfType = PsiTreeUtil.getParentOfType(this, XmlDocument.class);
      if (parentOfType == null) {
        return null;
      }
      return parentOfType.getDefaultNSDescriptor(namespace, strict);
    }

    return parentTag.getNSDescriptor(namespace, strict);
  }
 @NotNull
 public XmlTag[] findSubTags(final String name, final String namespace) {
   final XmlTag[] subTags = getSubTags();
   final List<XmlTag> result = new ArrayList<XmlTag>();
   for (final XmlTag subTag : subTags) {
     if (namespace == null) {
       if (name.equals(subTag.getName())) result.add(subTag);
     } else if (name.equals(subTag.getLocalName()) && namespace.equals(subTag.getNamespace())) {
       result.add(subTag);
     }
   }
   return ContainerUtil.toArray(result, new XmlTag[result.size()]);
 }
  @Nullable
  protected XmlElementDescriptor computeElementDescriptor() {
    for (XmlElementDescriptorProvider provider :
        Extensions.getExtensions(XmlElementDescriptorProvider.EP_NAME)) {
      XmlElementDescriptor elementDescriptor = provider.getDescriptor(this);
      if (elementDescriptor != null) {
        return elementDescriptor;
      }
    }

    final String namespace = getNamespace();
    if (XmlUtil.EMPTY_URI.equals(namespace)) { // nonqualified items
      final XmlTag parent = getParentTag();
      if (parent != null) {
        final XmlElementDescriptor descriptor = parent.getDescriptor();
        if (descriptor != null) {
          XmlElementDescriptor fromParent = descriptor.getElementDescriptor(this, parent);
          if (fromParent != null && !(fromParent instanceof AnyXmlElementDescriptor)) {
            return fromParent;
          }
        }
      }
    }

    XmlElementDescriptor elementDescriptor = null;
    final XmlNSDescriptor nsDescriptor = getNSDescriptor(namespace, false);

    LOG.debug(
        "Descriptor for namespace "
            + namespace
            + " is "
            + (nsDescriptor != null ? nsDescriptor.getClass().getCanonicalName() : "NULL"));

    if (nsDescriptor != null) {
      if (!DumbService.getInstance(getProject()).isDumb()
          || DumbService.isDumbAware(nsDescriptor)) {
        elementDescriptor = nsDescriptor.getElementDescriptor(this);
      }
    }
    if (elementDescriptor == null) {
      return XmlUtil.findXmlDescriptorByType(this);
    }

    return elementDescriptor;
  }