Brief history of HTML, XML and XHTML

Release: 2008-01-27
Jump to Web Standards Articles TOC

Markup

In the dawn of styled information, when typing meant using typewriters, the content also had written markings to describe parts of a document such as emphasis, layout and comments.

Today written markings or 'markup' are used practically everywhere. You may not even be aware that you are using it! For example today's word processing applications such as Microsoft Word, Microsoft Excel, Corel Wordperfect, all use markup languages to describe your stylizations and layouts with keywords such as bold, italic, tables and lists.

An International Standard of describing Markup Languages is SGML - Standard Generalized Markup Language. This is a robust technical language that is used to create technical project documentation and other information documents.

What are elements, attributes and entities in a Markup Language?

(If you already know, you can skip this section)

Markup information are the keywords encapsulated or enclosed within a set of pointy brackets '<' and '>'.
An example could be that a sentence The dog ran across the road, barking. Could be enhanced by markup:

The <animal>dog</animal> ran across the road, <strong>barking</strong>.

Here, dog has been described with the keyword of 'animal' - it is an animal. Also the word barking has been enhanced by the markup of 'strong' stating that it is strongly emphasized. Usually markup have a start 'tag' (<strong>) and an end 'tag' (</strong>) surrounding the text in question. This together is an Element.
Markup is used for document structure. Some elements such as line breaks don't contain any main text so could only require a start tag or 'Empty Element'. For instance:

For the first time this letter had been

styled to provide increased readability.

Would be marked up as:

"For the first time this letter had been<linebreak>styled to provide increased readability."

Comments could be marked up by <comment>This is a comment</comment>. But SGML provides a standard comment syntax:

-- This is an SGML comment --

These comments cannot have two dashes within the comment because the processor (or parser) would think you are ending the comment before you intended. These comments are used within elements but are typically within its own special Empty Element:

Attributes provide extra information to the element or empty element by having name="value" pairs within the start tag or empty element after the keyword.
For example:

<object data="images/display.png" type="image/png" width="22" height="22">

  A Portable Network Graphic

</object>

An entity reference, or entity, refers to a string of characters like a variable in a programming language. So you could have a commonly used line of text and put it into an entity then just use the entity throughout the document. Usually a set of entities can be declared for a document and each entity refers to a character in the current character set to make sure that a document displays the right character properly. Entities can take the form of a numbered entity: m or a hex entity: © or even a named entity: ©. Each of those three entity references would produce a copyright symbol: ©.

Continuing Markup

In applications such as Microsoft Word, Corel Wordperfect and Microsoft Wordpad markup is used behind the scenes: selecting a word and then activating the bold button or menu item makes the word appear bold. When you activated the button or menu item, the application wrapped the word in a markup element for applying bold styles which is visually interpreted as changing the word to appear bold.

SGML has been used to develop various markup languages such as Rich Text, Cold Fusion and also one of the most popular Internet information documents: HTML (HyperText Markup Language).

HTML was invented by Tim Burners-Lee (now in charge of the World Wide Web Consortium (W3C)) and then a new set of formal specifications developed by the Internet Engineering Task Force (IETF). Later passed the baton to the World Wide Web Consortium (W3C), gained more and more presentational elements and attributes. Also web browser vendors started adding non-standard, browser-specific markup to try and compete with other browser organizations which began a race of buggy, insecure, inaccessible, things rendering differently, poor excuse for web browsers. Finally the global community of Web Designers, Web Developers and general web users in discussion with browser vendors and the W3C began an initiative for Web Standards.

HTML goes standard and rakes in accessibility and extensibility

From version 4, HTML embraces Web Standards including accessibility. Providing a strict flavour that cuts out support for most presentational and other depreciated markup and forces proper structure rules. Strict flavour is to be used with Cascade Stylesheets which provide a more realistic way of providing presentation and layout to HTML documents. A Transitional and Frameset flavours allow the use of presentational and depreciated markup. But all three have features for alternative content for non-text material and support for internationalization.

eXtensible Markup Language

Browser vendors were screaming to have an easier way of adding more Markup that doesn't break Web Standards and generally in the Information Technology domain wanting a standard flexible document exchange format. The Web community with W3C developed a specification that is a strict subset of SGML: XML (eXtensible Markup Language). Even though it is smaller, the spec is strict to continue the power to create flexible Markup Languages. The strict structure rules include normal elements must have a start and end tag, empty elements are defined with a slash before the ending pointy bracket as <linebreak/> (empty elements can be a normal element too as long as there is absolutely nothing for the element content), attribute values must always be quoted and comments must only be used within its own special empty element: . Also as most SGML documents like HTML are case-insensitive: don't care if the element or attribute names are uppercase, lowercase or mixed, XML does care about the casing: is case sensitive.
Each element cannot have more than one attribute with the same name and an entity reference must be any of the three forms Named Entity, Hex Entity or Numbered Entity such as ' (if defined), ', '.
This allows a flexible construct to create markup languages where the XML Author can define their own XML Document elements and attributes. This is the foundation of XML.

eXtensible HTML

As more and more Markup Languages based on XML were popping up from W3C and other companies; a consensus was brought to update and refine HTML into the XML domain. XHTML, eXtensible HyperText Markup Language, does exactly that. The first version is basically the last HTML version (4.01) exposed as an XML language obeying the strict rules of XML but also basking in the benefits of a more solid structure (less error-prone), standard language and space handling, native Unicode support and bound to a Namespace allowing other XML structures to be used in the same document.
The XHTML Namespace URI is: http://www.w3.org/1999/xhtml and is usually a Default Namespace.

Coding in XHTML 1.0 and following the HTML Compatibility Guidelines will make your webpages not only backwards compatible - browsers that don't support native XHTML, or even XML will process it as HTML; but it is also forwards compatible - already well-formed and valid XML which will allow you to use any XML editing tool or any XML/native XHTML -only browsers currently and in the future plus being ready for newer XHTML versions.

Further XHTML versions include XHTML Basic which is the consensus choice for current and future mobile Internet and low-process Internet. XHTML Basic is made up with the minimal XHTML Modules from the Modular XHTML Collection - breaking up the language into more appropriate modules allows document authors to subset or extend XHTML with other modules and other XML-based languages. XHTML 1.1 is a typical XHTML Family specification using the standard set of modules and is a refined XHTML 1.0 Strict. All Modular XHTML like Basic and version 1.1 are native XHTMlL - processed by most XML supported browsers. Currently the W3C are developing XHTML 2 which is the ultimate XHTML specification with true accessibilities including a better way of handling non-text features and use of other XML languages such as XForms and XML Events.

Web Standards Articles TOC

Interesting Links for Web Standards Articles

Depreciated but archived:

Legend Scrolls