Section 1.2. Current Web Standards

1.2. Current Web Standards

Okay, so standards are great, but what standards are we talking about? This section looks at the current standards for the structural, presentational, and behavioral aspects of web design.

Web design and development is commonly discussed in terms of "layers" (and sometimes, even as a "layer cake," which is more enticing), borrowing a layer model from one commonly used for describing network protocols. The marked up document forms the structural layer, which is the foundation on which other layers may be applied. Next comes the presentation layer, specified with Cascading Style Sheets, that provides instructions on how the document should look on the screen, sound when it is read aloud, or be formatted when it is printed. On top of these layers, there may also be a behavioral layer , the scripting and programming that adds interactivity and dynamic effects to a site. This edition of Web Design in a Nutshell is organized according to this new mental model of web design.

The following is a summary of web technology Recommendations (what the W3C calls its final published standards) as of this writing. You can check in with further developments of these technologies at the W3C site (www.w3.org).

1.2.1. Structural Layer

After years of browser developers getting jiggy with tag creation, the web community is returning to HTML's original intent as a markup language: to describe the structure of the document, not to provide instructions for how it should look. The structural markup of the document forms the foundation on which the presentational and behavioral layers may be applied.

These are the current standard languages for structural markup:

XHTML 1.0 (Extensible Hypertext Markup Language) and XHTML 1.1

XHTML 1.0 is simply HTML 4.01 rewritten according to the stricter syntax rules of XML. XHTML 1.1 finally does away with deprecated and legacy elements and attributes and has been modularized to make future expansions easier. XHTML 2.0 is currently in development. The last version of HTML was HTML 4.01, which is still universally supported by today's browsers, but is not forward compatible. Part II looks at these languages in detail. Links to the full XHTML 1.0, XHTML 1.1, and HTML 4.01 specifications can be found on this page: www.w3.org/MarkUp/.

XML 1.0 (Extensible Markup Language)

XML is a set of rules for creating new markup languages. It allows developers to create custom tag sets for special uses. See Chapter 7 for more information, or go to the source at www.w3.org/XML/.

1.2.2. Presentation Layer

Now that all presentation instructions have been removed from the markup standard, this information is the exclusive job of Cascading Style Sheets. Style sheets standards are being developed in phases, as follows.

Cascading Style Sheets (CSS) Level 1

This style sheet standard has been a Recommendation since 1996 and is now fully supported by current browser versions. Level 1 contains rules that control the display of text, margins, and borders.

CSS Level 2.1

This Recommendation is best known for the addition of absolute positioning of web page elements. Level 2 reached Recommendation status in 1998, and the 2.1 revision is a Candidate Recommendation as of this writing. Support for CSS 2.1 is still inconsistent in current browser versions.

CSS Level 3

Level 3 builds on Level 2 but is modularized to make future expansion simpler and to allow devices to support logical subsets. This version is still in development.

You can find links to all three CSS specifications on this page: www.w3.org/Style/CSS. Style sheets are discussed further in Part III in this book.

1.2.3. Behavioral Layer

The scripting and programming of the behavioral layer adds interactivity and dynamic effects to a site.

1.2.3.1. Object models

The Document Object Model (DOM) allows scripts and applications to access and update the content, structure, and style of a document by formally naming each part of the document, its attributes, and how that object may be manipulated. In the beginning, each major browser had its own DOM, making it difficult to create interactive effects for all browsers.

Document Object Model (DOM) Level 1 (Core)

This version covers core HTML and XML documents as well as document navigation and manipulation. The DOM Level 1 Specification can be found at w3c.org/TR/REC-DOM-Level-1/.

DOM Level 2

Level 2 includes a style sheet object model, making it possible to manipulate style information. Links to the core and other modules of the DOM Level 2 Specification are available at www.w3.org/DOM/DOMTR.

1.2.3.2. Scripting

Netscape introduced its web scripting language, JavaScript, with its Navigator 2.0 browser. It was originally called "Livescript" but was later co-branded by Sun, and "Java" was added to the moniker. Microsoft countered with its own JScript while supporting some level of JavaScript in its Version 3.0 browser. The need for a cross-browser standard was clear.

JavaScript 1.5/ECMAScript 262

The W3C is developing a standardized version of JavaScript in coordination with the Ecma International, an international industry association dedicated to the standardization of information and communication systems. According to the Mozilla site, Netscape's JavaScript is a superset of the ECMAScript standard scripting language, with only mild differences from the published standard. In general practice, most developers simply refer to "JavaScript," and the standard implementation is implied.

The full specification can be found at www.ecma-international.org/publications/standards/Ecma-262.htm.

1.2.4. Other XML-Based Technologies

XML is a meta-language used to create other markup languages and applications. This powerful tool has enabled the development of some specialized standards. These are just a few. To see other XML technologies, visit the W3C site. With the modularization of XHTML and other XML specifications, it may be possible to mix and match XML modules within a single document, for example: XHTML, SVG, and MathML.

SVG 1.1 (Scalable Vector Graphics)

This is an XML language for defining two-dimensional vector and mixed vector/raster graphics. SVG is discussed briefly in Chapter 7. For in-depth information, read the specification at www.w3.org/TR/SVG11/.

MathML 2.0 (Mathematical Markup Language)

Just as it sounds, this is an XML language for defining the elements of mathematical notation, in both structure and content, for mathematics to be communicated and processed on the Web. More information and the specification can be found at www.w3.org/Math/.

SMIL 1.0 (Synchronized Media Integration Language) and SMIL 2.0

SMIL is an XML language for creating multimedia presentations that combine images, text, audio, and video in timed displays. More information and specifications can be found at www.w3.org/AudioVideo/.