Document Object Model
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Legacy DOM 
Legacy DOM was limited in the kinds of elements that could be accessed. Form, link and image elements could be referenced with a hierarchical name that began with the root document object. A hierarchical name could make use of either the names or the sequential index of the traversed elements. For example, a form input element could be accessed as either "document.formName.inputName" or "document.forms.elements."
The Legacy DOM enabled client-side form validation and the popular "rollover" effect.
Intermediate DOM 
After the release of ECMAScript, W3C began work on a standardized DOM. The initial DOM standard, known as "DOM Level 1," was recommended by W3C in late 1998. About the same time, Internet Explorer 5.0 shipped with limited support for DOM Level 1. DOM Level 1 provided a complete model for an entire HTML or XML document, including means to change any portion of the document. Non-conformant browsers such as Internet Explorer 4.x and Netscape 4.x were still widely used as late as 2000.
DOM Level 4 is currently being developed. Draft version 6 was released in December 2012.
By 2005, large parts of W3C DOM were well-supported by common ECMAScript-enabled browsers, including Microsoft Internet Explorer version 6 (from 2001), Opera, Safari and Gecko-based browsers (like Mozilla, Firefox, SeaMonkey and Camino).
Web browsers 
Because DOM supports navigation in any direction (e.g., parent and previous sibling) and allows for arbitrary modifications, an implementation must at least buffer the document that has been read so far (or some parsed form of it).
Layout engines 
Web browsers rely on layout engines to parse HTML into a DOM. Some layout engines such as Trident/MSHTML and Presto are associated primarily or exclusively with a particular browser such as Internet Explorer and Opera respectively. Others, such as WebKit and Gecko, are shared by a number of browsers, such as Google Chrome, Firefox and Safari. The different layout engines implement the DOM standards to varying degrees of compliance.
- Xerces is a collection of DOM implementations written in C++, Java and Perl
APIs that expose DOM implementations:
- JAXP (Java API for XML Processing) is an API for accessing DOM providers
See also 
- Ajax—a methodology employing DOM in combination with techniques for retrieving data without reloading a page.
- Application Object Model
- DOM scripting
- JDOM—a Java-based document object model for XML that integrates with DOM and SAX and uses parsers to build the document.
- RapidXml—is an attempt to create the fastest XML parser possible using modern C++.
- SAX—serial access parser API for XML, an alternative to DOM.
- SXML—a model for representing XML and HTML in the form of S-expressions.
- TinyXml—efficient platform-independent XML library for C++.
- "Document Object Model (DOM)". http://www.w3.org/: W3C. Retrieved 2012-01-12. "The Document Object Model is a platform- and language-neutral interface that will allow programs and scripts to dynamically access and update the content, structure and style of documents."
- Koch, Peter-Paul (May 14, 2001). "The Document Object Model: an Introduction". Digital Web Magazine. Retrieved January 10, 2009.
- Le Hégaret, Philippe (2002). "The W3C Document Object Model (DOM)". World Wide Web Consortium. Retrieved January 10, 2009.
- Guisset, Fabian. "What does each DOM Level bring?". Mozilla Developer Center. Mozilla Project. Retrieved January 10, 2009.
|Wikimedia Commons has media related to:
Document object models
- Document Object Model by the World Wide Web Consortium
- Technology Reports
- What does your user agent claim to support?
- W3C DOM scripts and compatibility tables (Quirksmode)
- Gecko DOM Reference (Mozilla Developer Center)
- XJR with DOM, SAX2, and XPath interfaces
- Firefox plugin that lets you visualize a Web's page DOM in 3D