DOM Specifications and DOM Node Interface

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∟DOM (Document Object Model) Programming Interface

∟DOM Specifications and DOM Node Interface

This section describes the DOM specification. The Core module in DOM Level 1, 2 and 3 specifications is for XML files. A tree of nodes is used to represent an XML file. Each node represents a unit of information in the XML file. All nodes are sharing the Node interface.

Currently, DOM has 4 levels of specifications:

DOM Level 0 - No formal specifications published: A collection of HTML document functionalities offered by Web browsers in 1996.
DOM Level 1 - Latest version published in 1998: Two modules: Core module is for XML documents; and HTML module for HTML documents.
DOM Level 2 - Published in 2000: 14 modules: Core, XML, HTML, Views, StyleSheets, CSS, etc.
DOM Level 3 - Published in 2004: 21 modules: Core, XML, HTML, XPath, Traversal, Range, Validation, etc.

Based the Core module of DOM Level 1 specification, an XML file is represented with a tree structure, called "document". Each node in the tree is a Node object, which represents a unit of information in the XML file.

A Node object is actually an instance of classes that implemented the Node interface, which contains these methods:

getNodeType(): Returns the node type.
getNodeName(): Returns the node name.
getNodeValue(): Returns the value associated with this node.
getChildNodes(): Returns a list of nodes nested inside this node.
getAttributes(): Returns a list of nodes that represents the attributes of this node.

DOM Level 1 Core module specifies these nodes types, each of them could be implemented as separated class:

 2 ATTRIBUTE_NODE
 4 CDATA_SECTION_NODE
 8 COMMENT_NODE
11 DOCUMENT_FRAGMENT_NODE
 9 DOCUMENT_NODE
10 DOCUMENT_TYPE_NODE
 1 ELEMENT_NODE
 6 ENTITY_NODE
 5 ENTITY_REFERENCE_NODE
12 NOTATION_NODE
 7 PROCESSING_INSTRUCTION_NODE
 3 TEXT_NODE