Table of contents

Appendices

B.4 Namespace URI Lookup

The following describes in pseudo code the algorithm used in the lookupNamespaceURI method of the Node interface. This methods ignores DOM Level 1 nodes.

DOMString lookupNamespaceURI(in DOMString prefix) 
{ 
  switch (nodeType) { 
     case ELEMENT_NODE: 
     { 
         if ( Element's namespace != null and Element's prefix == prefix ) 
         { 
               // Note: prefix could be "null" in this case we are looking for default namespace 
               return (Element's namespace);
         } 
         if ( Element has attributes)
         { 
            for ( all DOM Level 2 valid local namespace declaration attributes of Element )
            {
                 if (Attr's prefix == "xmlns" and Attr's localName == prefix ) 
                       // non default namespace
                 { 
                        if (Attr's value is not empty) 
                        {
                          return (Attr's value);
                        }         
                        return unknown (null);                   
                 } 
                 else if (Attr's localname == "xmlns" and prefix == null)
                       // default namespace
                 { 
                        if (Attr's value is not empty) 
                        {
                          return (Attr's value);
                        }         
                        return unknown (null); 
                 } 
           }
         } 
         if ( Element has an ancestor Element ) 
            // EntityReferences may have to be skipped to get to it 
         { 
                   return ancestorElement.lookupNamespaceURI(prefix); 
         } 
         return null; 
     } 
     case DOCUMENT_NODE: 
          return documentElement.lookupNamespaceURI(prefix) 

     case ENTITY_NODE: 
     case NOTATION_NODE: 
     case DOCUMENT_TYPE_NODE: 
     case DOCUMENT_FRAGMENT_NODE: 
           return unknown (null); 

     case ATTRIBUTE_NODE: 
         if (Attr has an owner Element) 
         { 
             return ownerElement.lookupNamespaceURI(prefix); 
         } 
         else 
         { 
             return unknown (null); 
         } 
     default: 
         if (Node has an ancestor Element) 
          // EntityReferences may have to be skipped to get to it 
         { 
             return ancestorElement.lookupNamespaceURI(prefix); 
         } 
         else { 
             return unknown (null); 
         } 
  } 
}