Document Object Model: Difference between revisions

Revision as of 18:20, 24 February 2004

Revision as of 17:10, 4 March 2004

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'''Document Object Model (DOM)''' is a form of representation of [[structured document]]s as an [[object-oriented]] model. DOM is the official [[World Wide Web Consortium]] (W3C) standard for representing structured documents in a platform- and language-neutral manner.

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DOM doesn't put restrictions on what the document's underlying [[data structure]] is. A well-structured document can take the [[tree structure|tree form]] using DOM. Most XML parsers (e.g., [[Xerces]]) and [[Extensible stylesheet language|XSL]] processors (e.g., [[Xalan]]) have been developed to make use of the tree structure. Such an implementation requires that the entire content of a document be parsed and stored in memory. Hence, DOM is best used for applications where the document elements have to be randomly-accessed and manipulated. For XML-based applications which involve a one-time selective read/write per parse, DOM presents a considerable overhead on memory. The [[SAX]] model is advantageous in such a case in terms of speed and memory consumption.

The custodian of the DOM is the [[World Wide Web Consortium]] (W3C). The current DOM specification is Level 2. Level 1 specification allowed for [[navigation]] of an HTML or XML document and to manipulate content. Level 2 came up with XML [[Namespace]] support, filtered views and events. Level 3 specification is (as of 2003) a working draft and still under development at the W3C.

===Web-browser incompatibilities===

A different DOM implementation from [[Microsoft]] has led to [[inter-operability]] problems for web browsers.

As Microsoft's [[Internet Explorer]] browser is, as of [[2004]], the de-facto standard web browser, this poses real problems for the developers of more standards-compliant browsers such as [[Mozilla]]. If they adopt the Microsoft extensions to the DOM, they risk losing any [[credibility]] in their calls for web-sites to become standards-compliant, and if they do not, they risk alienating their users by losing much or all of the content of web-sites which use the non-standard extensions. Cynics regard this as another case of Microsoft applying [[embrace, extend and extinguish]] tactics. This could be considered ironic, as both Microsoft and [[Netscape]] were guilty of supplying non-standard features in an arms-race for standards control, and Mozilla was born out of a Netscape initiative.

The general consensus appears to be that this will only change if new standards-compliant browsers gain a significant market-share on the Web, thus making the use of non-standard extensions a commercial problem for the authors of non-standards-compliant websites.

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Internet Explorer 7.0 is rumoured to likely be more standards-compliant in its implementation of the DOM, but is unlikely to pull support for the current proprietary DOM extensions.

===See also===

* [[SAX]] - a set of APIs for accessing and manipulating XML documents in a sequential manner.

* [[JDOM]] - a Java-based document object model for XML that integrates with DOM and SAX and uses parsers to build the document.

'''==External Links:'''links==

*[http://www.w3.org/DOM/ - W3.org on DOM]

*[http://wwwxml.mozillacoverpages.org/docs/dom/domref/ -.html MozillaTechnology DOMReports]

*[http://www.mozilla.org/docs/dom/domref/ Gecko DOM Reference]

*[http://msdn.microsoft.com/library/default.asp?url=/workshop/author/dom/domoverview.asp About the W3C Document Object Model]

[[de:Document Object Model]]

[[es:DOM]]

[[fr:Document object model]]

[[ja:Document Object Model]]

[[pl:DOM]]