Overview of XHTML:
XHTML 2.0 is a markup language developed for rich and portable web-based applications. Although XHTML 2.0 is derived from XHTML 1.0, XHTML 1.1, and HTML 4, it is not purported to provide 100 % backwards compatibility to its earlier versions. Web-based application developers who are familiar with its predecessors will be comfortable with working on XHTML 2.0. Also, XHTML 2.0 has been a member of the XHTML Family of markup languages. Moreover, it is an XHTML Host Language defined in the Modularization of XHTML. It is comprised of a set of XHTML modules which describe the attributes and elements of the language, along with their content model. It also updates most of the modules defined in Modularization of XHTML including the updated versions of those modules and their semantics.
XHTML 2.0 is exclusively based on XML, wherein SGML heritage and syntax peculiarities that existed in the current web markup are eliminated. Technically, XHTML 2.0 is a "general-purpose" language comprising of a minimum default feature set that is easily extendible by using CSS and other similar technologies like XML Events, XForms, etc. moreover, it is a modular approach allowing the XHTML 2 working group to concentrate on generic document markup, whereas other technologies employ several mechanisms for document construction, interactivity, presentation, etc. Furthermore, the number one priority for the XHTML group is to promote further separation of document content as well as structure extracted from document presentation. Moreover, other goals of XHTML 2.0 working group is to increase accessibility and usability, device independence, better internationalization, improved integration with the Semantic Web.
XHTML 2.0 was developed shortly after XHTML 1.1 was broadly recommended in 2001, followed by the release of the very first XHTML 2.0 working draft in 2002. However, most of the documentation was in an incomplete, non-standardized state. Some outstanding industry stakeholders, like web developers, browser vendors, content owners, and designers, by 2004, had been dissatisfied with the way XHTML2 working group was shaping up. Referring to the closed behavior and nature of the W3C processes, they settled on starting over and developing their own standard. Hence, in 2004, Web Hypertext Application Technology Working Group (WHATWG) was formed as an independent coalition. The group commenced operations on a specification known as Web Applications 1.0. The W3C's overwhelming votes, in April 2007, was inclined more towards the proposal of adopting the group's specification for reviewing. However, the original members of WHATWG started operating in the W3C as the independent HTML working group. The members continued to develop their proposal that was then renamed as HTML 5. Therefore, there is a possibility that the working draft of HTML 5 group may become a recommendation for W3C along with XHTML 2.0.
The XHTML 2 working group does not clearly deal with backward compatibility as compared to their predecessors, including the HTML working group. This has, thereby, led them to neglect many of the syntactic packages that existed in earlier versions of HTML. As a result, a cleaner, and a more concise language was developed that accurately detects and corrects most of the past indiscretions of Web markup.
The objective of XHTML 2 working group is to satisfy the need for applying XHTML to a broad array of varying platforms with more focus thrown on internationalization, device impendence, accessibility, document structuring and usability. The XHTML group provides a significant piece for supporting rich, robust and quality Web content that effectively combines XHTML with several other W3C work on areas like scalable vector graphics, math, forms, and synchronized multimedia, in coordination with other W3C working groups.
The XHTML 2.0 group specifies the usage of the "backward compatible" under the following conditions:
- The external interface to the module cannot be changed in any way which would lead to breaking of either markup language or another module.
- The content model cannot be changed in any way by which a previously valid document would become invalid.
If incase either of the above mentioned constraints is violated by a change, the XHTML 2.0 working group will either not make the change or amend the applicable module. The latter case will lead to changes in the associated identifiers as well.
The XHTML 2 working group has recently published the second edition of the Group Note of XHTML Media Types. Several customers wish to use XHTML to create their web pages. However, they are unclear and confused about the most effective ways of delivering those pages in a way to be processed correctly by several user agents. Furthermore, included in this Note are the suggestions regarding how the formatting of XHTML is done to ensure it is portable, and the ways of delivering XHTML to a variety of user agents. The mission of this document is to be used by various document authors who wish to use XHTML, but are not confident that the XHTML content they developed is likely to work in varying platforms and environments.
The focus of XHTML 5 is mainly on creation of a more generic, user-friendly, and simplified language. They've refrained from introducing several specialized elements to show different types of content. The working group also argued that the new role attribute offers a mechanism by which rich metadata can be included, by making the need for specialized elements, insignificant. For this, a few new elements were included such as blockcode for computer code, di for a group of related definitions and terms in dl, for multiple spellings, or multiple definitions, and handler for scripted event handlers, with a kind of attribute indicating the handler language.Overview of HTML 5:
Unlike XTHML 2.0 that aimed to be revolutionary, HTML 5 was designed as an evolutionary technology since the HTML working group took more pragmatic measures and approaches. In other words, HTML 5 can be stated as an incremental step taken for remaining most compatible with the current XHTML 1/ HTML 4 standards. Nevertheless, HTML 5 provides several number of changes and extensions to XHTML 1/ HTML 4 standards that deal with most of the errors in the earlier specifications.
Interestingly, HTML 5 is concerned with shifting HTML from the document markup, and converting it into a language compatible for web applications. A greater amount of specification deals with creating a feature-full and more robust client side environment for development of web application by offering a number of varying APIs. Amongst other things, the specification defines that following implementations should provide persistent storage for client-side, including SQL storage engines and key/value, video and audio playback APIs, cross-document messaging, 2D drawing using the canvas element, a networking API, and server-sent events.
Additionally, the HTML 5 specification aims at maintaining an SGML-like syntax which is compatible with the specifications of the current HTML, even though it no longer supports the more private features of SGML. A second "XML Serialization" is also included in the specification that allows application developers to serve XML documents. Again, the HTML working group has discovered a balance between progress and pragmatism by preserving an SGML-like serialization. Moreover, developers can markup content by using either the XML serialization (appearing similar to XHTML 1.x) or the HTML serialization (appearing similar to HTML 4.x).
Since XHTML 2.0 employs a new HTML vocabulary with improvised features of multimedia content, hyperlinks, declarative interactive forms, rich metadata, as well as demonstrating the semantics of human literary works like scientific papers and poems.
However, it is deprived of the elements for describing and expressing the semantics of most of the non-document types of content seen on the Web. A good example of this is auction sites, forum sites, online shops, search engines, etc, which are not well versed with document metaphor, and not covered by XHTML 2.0. Moreover, this specification aims at extending HTML. XHML 2 and HTML 5 specification utilize different namespaces, and hence, can be implemented within the same XML processor.
Lately, W3C has also launched the HTML 5 Japanese Interest Group which targets at facilitating focused and in-depth discussion in Japanese of the HTML 5 specification along with specifications tightly related to HTML 5, for gathering question, comments, and feedbacks in Japanese regarding those specifications, for collecting information about particular use cases in Japan only for technologies specified in those specifications, and lastly, for reporting the outcomes of its activities as a team or group and others within the community.
Many new elements have been added by HTML 5 that are not available in XHTML 2.0., such as figure representing a graphic or an image with a caption, a nested legend representing the caption, whereas a normal img element used for the image; time representing time and date; m representing marked text; meter indicating measurements, datagrid indicating an interactive tree list or tabular information/data; etc. HTML 5 also provides an API for offline web applications similar to Google Gears. Also, an editing API is also included that may be used in combination with the global attribute 'contenteditable'. HTML 5 also has a provision for allowing Web applications to interact with each other through the TCP through a network API.
In addition, various types of new attributes help in order to semantically markup the portions of a document. These self-explanatory elements include article, section, header, footer, aside, etc. Also, a new dialog element is introduced for representing the communication and conversation by using dd elements for the text and child dt elements indicating the speaker's name.
As an attempt to accelerate the development of HTML 5, World Wide Web Consortium had announced that it would terminate all XHTML 2 research. This meant that the XHTML 2.0 working group would discontinue all its activities by the end of 2009 and the resulting resources were re-directed to the HTML 5 working group.
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