The DocumentType interface is defined in the W3C Document Object Model (DOM) Level 2 Core Specification. (Refer to http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113.)

Each Document has a doctype attribute whose value is either null or a DocumentType object. The DocumentType interface in the DOM Core provides an interface to the list of entities that are defined for the document, and little else because the effect of namespaces and the various XML schema efforts on DTD representation are not clearly understood as of this writing.

The DOM Level 2 doesn't support editing DocumentType nodes.