The main part of the DOM API Level 1 is a set of core interfaces, which is a must for any DOM API implementation. The core interfaces contain methods useful for any type of tree-structured document as well as some XML-specific extensions.
In addition to core interfaces, the specification defines an API for accessing HTML document trees.
The DOM Level 1 Core Interfaces Specification defines two types of interfaces:
Fundamental— Ones that should be realized in any DOM Level 1–compliant implementation.
Extended— Interfaces that are not required in some implementations—for example, in HTML-only implementations of DOM Level 1.
The W3C specification of DOM gives Interface Definition Language (IDL) definitions of interfaces ...