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);
  }
 public PomModelEvent runInner() throws IncorrectOperationException {
   final ASTNode anchor = expandTag();
   if (myChild.getElementType() == XmlElementType.XML_TAG) {
     // compute where to insert tag according to DTD or XSD
     final XmlElementDescriptor parentDescriptor = getDescriptor();
     final XmlTag[] subTags = getSubTags();
     final PsiElement declaration =
         parentDescriptor != null ? parentDescriptor.getDeclaration() : null;
     // filtring out generated dtds
     if (declaration != null
         && declaration.getContainingFile() != null
         && declaration.getContainingFile().isPhysical()
         && subTags.length > 0) {
       final XmlElementDescriptor[] childElementDescriptors =
           parentDescriptor.getElementsDescriptors(XmlTagImpl.this);
       int subTagNum = -1;
       for (final XmlElementDescriptor childElementDescriptor : childElementDescriptors) {
         final String childElementName = childElementDescriptor.getName();
         while (subTagNum < subTags.length - 1
             && subTags[subTagNum + 1].getName().equals(childElementName)) {
           subTagNum++;
         }
         if (childElementName.equals(
             XmlChildRole.START_TAG_NAME_FINDER.findChild(myChild).getText())) {
           // insert child just after anchor
           // insert into the position specified by index
           if (subTagNum >= 0) {
             final ASTNode subTag = (ASTNode) subTags[subTagNum];
             if (subTag.getTreeParent() != XmlTagImpl.this) {
               // in entity
               final XmlEntityRef entityRef =
                   PsiTreeUtil.getParentOfType(subTags[subTagNum], XmlEntityRef.class);
               throw new IncorrectOperationException(
                   "Can't insert subtag to the entity. Entity reference text: "
                       + (entityRef == null ? "" : entityRef.getText()));
             }
             myNewElement =
                 XmlTagImpl.super.addInternal(myChild, myChild, subTag, Boolean.FALSE);
           } else {
             final ASTNode child = XmlChildRole.START_TAG_END_FINDER.findChild(XmlTagImpl.this);
             myNewElement = XmlTagImpl.super.addInternal(myChild, myChild, child, Boolean.FALSE);
           }
           return null;
         }
       }
     } else {
       final ASTNode child = XmlChildRole.CLOSING_TAG_START_FINDER.findChild(XmlTagImpl.this);
       myNewElement = XmlTagImpl.super.addInternal(myChild, myChild, child, Boolean.TRUE);
       return null;
     }
   }
   myNewElement = XmlTagImpl.super.addInternal(myChild, myChild, anchor, Boolean.TRUE);
   return null;
 }