W3C DOM - slide "Document Interface Methods"

Attr createAttribute(String name)
Creates an attribute of the given name
Element createElement(String tagName)
Creates an element of the type given
Text createTextNode(String data)
Creates a Text Node
Element getDocumentElement()
Gets the root element of the document
Element getElementById(String elementId) Get the element with the given ID
NodeList getElementsByTagName(String tagname)
Returns a NodeList of all the elements with a given tag name