DOM Level 2

DOM Level 2
Name	DOM Level 2
Status	Historic W3C Recommendation
Domain	Web APIs
Initial release	2000
Developer	World Wide Web Consortium
Related	Document Object Model, XML, HTML

DOM Level 2 DOM Level 2 is a W3C specification that extended the original Document Object Model to add standardized interfaces for World Wide Web Consortium, XML, HTML, CSS, XPath, SVG, and XSLT processing. It provided API improvements adopted by vendors including Netscape Communications Corporation, Microsoft, Mozilla Foundation, Opera Software, and Apple Inc. and influenced implementations in projects such as Apache Software Foundation servers and GNU toolchains. The specification shaped web platform capabilities used by developers working with browsers like Internet Explorer, Firefox, Chrome, Safari, and Opera.

Overview

DOM Level 2 was published as an advancement of the original DOM work under the aegis of the World Wide Web Consortium and contributions from organizations including W3C Consortium Member, Netcraft, Sun Microsystems, IBM, Netscape Communications Corporation, and Microsoft. The specification is organized into modules to separate concerns for document traversal, events, ranges, styles, and views, enabling interoperability among implementations in Mozilla Foundation products, Apple Inc. WebKit, and Opera Software engines. It provided extension points for languages and technologies like ECMAScript, Java, DOM Level 3, XForms, and SVG authoring.

Specifications and Modules

The DOM Level 2 set comprises multiple modules standardized to cover different aspects of client-side document manipulation. Notable modules include: - Core: defines the DOM tree and node interfaces influencing libraries like Apache Xerces, libxml2, and Oracle Corporation XML parsers. - Views: defines document views and document-related metrics used by applications from Adobe Systems and Sun Microsystems. - Events: standardized event flow and listeners used by frameworks from Google LLC and projects like jQuery and Prototype JavaScript Framework. - Style: provided interfaces to access CSS information, relevant to Cascading Style Sheets authors and engines in WebKit and Gecko. - Traversal and Range: specified efficient node navigation and document fragment manipulation adopted by Document Object Model implementations in Mozilla Foundation and Microsoft products.

The modular approach allowed integration with technologies such as XPath for node selection and XSLT for transformations found in SAX and DOMParser implementations maintained by organizations like Apache Software Foundation and Eclipse Foundation.

History and Development

Work on DOM Level 2 followed the initial DOM Level 1 recommendations and was driven by interoperability needs voiced by browser vendors and standards bodies including World Wide Web Consortium working groups and contributors from Netscape Communications Corporation, Microsoft, Sun Microsystems, IBM, Apple Inc., and Opera Software. Drafts were iterated through community feedback processes involving stakeholders such as IETF, ECMA International, W3C Advisory Committee, and independent contributors associated with projects like GNOME and KDE. The evolution of DOM Level 2 paralleled advances in HTML 4.01 and influenced later specifications like DOM Level 3 and HTML5.

Implementation and Browser Support

Major browser engines implemented large portions of DOM Level 2 to varying degrees. Microsoft implemented event and traversal features in Internet Explorer releases, while Mozilla Foundation incorporated modules into Firefox and standalone libraries like SpiderMonkey. Apple Inc. added support in Safari via WebKit, and Opera Software provided implementations in its Presto engine and later Blink-based versions. Server-side projects such as Apache Tomcat, Jetty, and Node.js-adjacent libraries used DOM Level 2 concepts within parsers like Xerces, libxml2, and NekoHTML. Support also extended into mobile platforms via engines used by Nokia, BlackBerry Limited, and Google Android early releases.

Key Features and Changes from DOM Level 1

DOM Level 2 introduced several significant capabilities beyond Level 1: - Event model: a standardized capturing and bubbling event flow similar to models used by Microsoft and Netscape Communications Corporation implementations, enabling libraries like Dojo Toolkit and Prototype to build cross-browser abstractions. - Views and style access: programmatic access to computed styles linked to Cascading Style Sheets processing in engines like Gecko and WebKit. - Namespaces: explicit XML namespace support aligning with XML Namespaces recommendations and used by SVG and MathML authors. - Ranges and traversal: precise document subrange manipulation leveraged by editors like Mozilla Thunderbird and web applications from Google LLC. - Modularization: clearer separation of concerns enabling adoption by server-side parsers from Apache Software Foundation and client-side frameworks like jQuery.

These changes facilitated richer web applications and influenced subsequent standards such as HTML5 and DOM Level 3.

Criticisms and Limitations

Despite its advances, DOM Level 2 faced criticism. Implementers and authors from projects like Mozilla Foundation, Opera Software, and Microsoft pointed to inconsistent cross-browser behavior and incomplete adoption of modules in products including Internet Explorer and early Safari builds. The specification’s complexity and partial overlaps with ECMAScript bindings led to fragmentation observed in libraries like jQuery and frameworks such as Dojo Toolkit. Interoperability issues prompted community efforts by organizations such as World Wide Web Consortium and WHATWG to streamline later specifications, culminating in work on DOM Level 3 and HTML5 to address deficiencies.

Category:Web standards