HTML 5

From Wikipedia

HTML5 is a language for structuring and presenting content for the World Wide Web, and is a core technology of the Internet originally proposed by Opera Software. It is the fifth revision of the HTML standard (created in 1990 and standardized as HTML4 as of 1997) and as of March 2012 is still under development. Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers, etc.). HTML5 is intended to subsume not only HTML 4, but XHTML 1 and DOM Level 2 HTML as well.

Following its immediate predecessors HTML 4.01 and XHTML 1.1, HTML5 is a response to the observation that the HTML and XHTML in common use on the World Wide Web are a mixture of features introduced by various specifications, along with those introduced by software products such as web browsers, those established by common practice, and the many syntax errors in existing web documents.It is also an attempt to define a single markup language that can be written in either HTML or XHTML syntax. It includes detailed processing models to encourage more interoperable implementations; it extends, improves and rationalises the markup available for documents, and introduces markup and application programming interfaces (APIs) for complex web applications. For the same reasons, HTML5 is also a potential candidate for cross-platform mobile applications. Many features of HTML5 have been built with the consideration of being able to run on low-powered devices such as smartphones and tablets. In December 2011 research firm Strategy Analytics forecast sales of HTML5 compatible phones will top 1 billion in 2013.

In particular, HTML5 adds many new syntactical features. These include the new <video>, <audio> and <canvas> elements, as well as the integration of Scalable Vector Graphics (SVG) content that replaces the uses of generic <object> tags. These features are designed to make it easy to include and handle multimedia and graphical content on the web without having to resort to proprietary plugins and APIs. Other new elements, such as <section>, <article>, <header> and <nav>, are designed to enrich the semantic content of documents. New attributes have been introduced for the same purpose, while some elements and attributes have been removed. Some elements, such as <a>, <cite> and <menu> have been changed, redefined or standardized. The APIs and document object model (DOM) are no longer afterthoughts, but are fundamental parts of the HTML5 specification. HTML5 also defines in some detail the required processing for invalid documents so that syntax errors will be treated uniforlly by all conforming browsers and other user agents.

History

The Web Hypertext Application Technology Working Group (WHATWG) began work on the new standard in 2004, when the World Wide Web Consortium (W3C) was focusing future developments on XHTML 2.0, and HTML 4.01 had not been updated since 2000. In 2009, the W3C allowed the XHTML 2.0 Working Group's charter to expire and decided not to renew it. W3C and WHATWG are currently working together on the development of HTML5.

Even though HTML5 has been well known among web developers for years, it became the topic of mainstream media in April 2010. after Apple Inc's then-CEO Steve Jobs issued a public letter titled "Thoughts on Flash" where he concludes that "[Adobe] Flash is no longer necessary to watch video or consume any kind of web content" and that "new open standards created in the mobile era, such as HTML5, will win". This sparked a debate in web development circles where some suggested that while HTML5 provides enhanced functionality, developers must consider the varying browser support of the different parts of the standard as well as other functionality differences between HTML5 and Flash. In early November 2011 Adobe announced that it will discontinue development of Flash for mobile devices and reorient its efforts in developing tools utilizing HTML 5.
Standardization process

The Mozilla Foundation and Opera Software presented a position paper at a World Wide Web Consortium (W3C) workshop in June 2004, focusing on developing technologies that are backwards compatible with existing browsers, including an initial draft specification of Web Forms 2.0. The workshop concluded with a vote, 8 for, 14 against, for continuing work on HTML. Later that month, work based upon that position paper moved to the newly formed Web Hypertext Application Technology Working Group (WHATWG), and a second draft, Web Applications 1.0, was also announced.The two specifications were later merged to form HTML5.

The HTML5 specification was adopted as the starting point of the work of the new HTML working group of the W3C in 2007. This working group published the First Public Working Draft of the specification on 22 January 2008. Parts of HTML5 have been implemented in browsers despite the whole specification not yet having reached final Recommendation status.

According to the original W3C timetable, it was estimated that HTML5 would reach W3C Recommendation by late 2010, after a Last Call in 2008. However, the First Public Working Draft estimate was missed by eight months, and Last Call was only reached in 2011.

On 14 February 2011, the W3C extended the charter of its HTML Working Group with clear milestones for HTML5. In May 2011, the working group advanced HTML5 to "Last Call", an invitation to communities inside and outside W3C to confirm the technical soundness of the specification. The W3C is developing a comprehensive test suite to achieve broad interoperability for the full specification by 2014, which is now the target date for Recommendation.

The criterion for the specification becoming a W3C Recommendation is "two 100% complete and fully interoperable implementations". In an interview with TechRepublic, Ian Hickson guessed that this would occur in the year 2022 or later. However, many parts of the specification are stable and may be implemented in products.

The WHATWG made a Last Call for its HTML5 specification in October 2009.[ Then, in December 2009, WHATWG switched to an unversioned development model for the HTML specification, effectively abandoning its HTML5 project, but kept the name "HTML5".In January 2011, following this, the WHATWG renamed its "HTML5" living standard to "HTML". The W3C nevertheless continues its project to release HTML5.

As of January 2012, the specification is in Working Draft state at the W3C. Ian Hickson of Google is the editor of HTML5.
Markup

HTML5 introduces a number of new elements and attributes that reflect typical usage on modern websites. Some of them are semantic replacements for common uses of generic block (<div>) and inline (<span>) elements, for example <nav> (website navigation block), <footer> (usually referring to bottom of web page or to last lines of HTML code), or <audio> and <video> instead of <object>. Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as <font> and <center>, whose effects are achieved using Cascading Style Sheets. There is also a renewed emphasis on the importance of DOM scripting in Web behavior.

The HTML5 syntax is no longer based on SGML despite the similarity of its markup. It has, however, been designed to be backward compatible with common parsing of older versions of HTML. It comes with a new introductory line that looks like an SGML document type declaration, <!DOCTYPE html>, which triggers the standards-compliant rendering mode. As of 5 January 2009, HTML5 also includes Web Forms 2.0, a previously separate WHATWG specification.

New APIs

In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs). Existing document object model (DOM) interfaces are extended and de facto features documented. There are also new APIs, such as:

The canvas element for immediate mode 2D drawing. See Canvas 2D API Specification 1.0 specification
Timed media playback
Offline Web Applications
Document editing
Drag-and-drop
Cross-document messaging
Browser history management
MIME type and protocol handler registration
Microdata
Web Storage, a key-value pair storage framework that provides behaviour similar to Cookies but with larger storage capacity and improved API.

Not all of the above technologies are included in the W3C HTML5 specification, though they are in the WHATWG HTML specification. Some related technologies, which are not part of either the W3C HTML5 or the WHATWG HTML specification, are as follows. The W3C publishes specifications for these separately:

· Geolocation.

· Web SQL Database, a local SQL Database (no longer maintained).

· The Indexed Database API, an indexed hierarchical key-value store (formerly WebSimpleDB).

· File API, Handle file uploads and file manipulation.

· Directories and System. This API is intended to satisfy client-side-storage use cases not well served by databases.

· File Writer. An API for writing to files from web applications.

HTML5 alone cannot provide animation within web pages. Either JavaScript or CSS3 is necessary for animating HTML elements. Animation is also possible using JavaScript and HTML 4, and within SVG elements through SMIL, although browser support of the latter remains uneven as of 2011.
XHTML5

XHTML5 is the XML serialization of HTML5. XML documents must be served with an XML Internet media type such as application/xhtml+xml or application/xml. XHTML5 requires XML's strict, well-formed syntax. The choice between HTML5 and XHTML5 boils down to the choice of a MIME/content type: the media type one chooses determines what type of document should be used. In XHTML5 the HTML5 doctype html is optional and may simply be omitted. HTML that has been written to conform to both the HTML and XHTML specifications—and which will therefore produce the same DOM tree whether parsed as HTML or XML—is termed "polyglot markup".
Error handling

An HTML5 (text/html) browser will be flexible in handling incorrect syntax. HTML5 is designed so that old browsers can safely ignore new HTML5 constructs.In contrast to HTML 4.01, the HTML5 specification gives detailed rules for lexing and parsing, with the intent that different compliant browsers will produce the same result in the case of incorrect syntax. Although HTML5 now defines a consistent behavior for "tag soup" documents, those documents are not regarded as conforming to the HTML5 standard.
Popularity

According to a report released on 30 September 2011, 34 of the world's top 100 Web sites were using HTML5 – the adoption led by search engines and social networks.