The DocumentType interface inherits from the Node interface and provides an interface to the list of entities that are defined for the document. Each Document has a doctype attribute whose value is either null or a DocumentType object. The DocumentType interface in the DOM Level 1 Core specifies an interface to the list of entities that are defined for the document, and little else because the effect of name spaces and the various XML scheme efforts on DTD representation are not yet clearly defined.
The DOM Level 1 specification doesn’t support editing DocumentType nodes.