The XHTML Family

Steven Pemberton

CWI, Amsterdam

Chair, W3C HTML Working Group

HTML as XML application

• Transition from 'old world' to XML
• Clean up (get rid of historical flotsam)
• Return to structure only
• Use generic XML as much as possible
• Modularise -- split into separate parts
• Add any required new functionality
• Address wider needs (International, Accessibility)
• Add new functionality

Plan of action

Phase 1:

• HTML 4.01: corrected version
• XHTML 1.0: transitional version of HTML 4.01 in 3 flavours

Phase 2:

• Modularisation: agreement on split and methodology
• XHTML Basic: Small devices
• XHTML 1.1: clean version of 1.0 strict, plus Ruby markup

(plan of action)

Phase 3:

• Events: accessible and device-independent
• Forms: more control
• Fix frames
• XHTML 2.0: Putting it all together

XHTML 1.0

• XHTML 1.0 is an XML-ised version of HTML 4.01
• Just like HTML 4.01, there are 3 versions: 'strict', 'transitional', and 'frameset'
• Carefully designed to make use of 'quirks' in existing HTML browsers, so that a small number of guidelines allows it to be served to both HTML and XML user agents
• Recommendation: January 2000; second edition planned
• Deployable on most existing browsers; native on Amaya, Opera, NS, Mozilla

XHTML Modularisation

• XHTML has been divided into a number of modules.
• A module is a parameterised collection of elements and/or attributes that can be used as building blocks to build a DTD. (Coming soon: Schema)
• A language can be built by using just XHTML modules, or adding your own
• Recommendation: April 2001
• Schemas First Working Draft: 22 March 2001

XHTML modules

• Structure: html, head, title, body
• Text: abbr, acronym, address, blockquote, br, cite, code, dfn, div, em, h1, h2, h3, h4, h5, h6, kbd, p, pre, q, samp, span, strong, var
• Hypertext: a
• List: ol, ul, dl, li, dt, dd

(modules)

• Applet (deprecated): applet, param
• Presentation: b, i, hr, big, small, sub, sup, tt
• Edit: del, ins
• Bi-directional Text: bdo

(modules)

• Basic Forms: simple forms
• Forms: full forms

• Basic Tables: simple tables
• Tables: full tables

(modules)

• Image: img
• Client-side Image Map: map, +
• Server-side Image Map: change to img
• Object: object, param
• Frames
• Target: attribute
• Iframe

(modules)

• Events: adds events attributes
• Metainformation: meta
• Scripting: script
• Stylesheet: style
• Style Attribute
• Link: link

(modules)

• Base: base
• Name Identification: name attribute
• Legacy: basefont, center, font, s, strike, u, plus loads of attributes (eg align)
• Ruby: East Asian markup

Note on modules

• Some modules consist of a single element, or just add some attributes to existing elements
• Not all modules are independent: if you use some modules, they bring other modules with them, or change other modules
• Future modules are planned (eg extended forms, events)

The XHTML family

• To be an XHTML host language you must use the Structure, Hypertext, Basic Text, and List modules
• To be an XHTML integration language you may define your own Structure module
• Example integration languages include SMIL+HTML, Math+HTML

XHTML Basic

• XHTML Basic is the first XHTML family-member to be defined using Modularisation
• Designed for small devices, e.g. mobile telephones
• Recommendation: December 2000
• Part of WAP2
• Already implemented on two handsets
• XHTML-Print plans

XHTML Basic Modules

Structure*, Text*, Hypertext*, List*, Basic Forms (form, input, label, select, option, textarea), Basic Tables (caption, table, td, th, tr), Image, Object, Meta, Link, Base.

XHTML 1.1

• XHTML 1.1 is the second family member to be defined using Modularisation
• It is a cleaned-up, non-legacy version of XHTML 1.0 strict (no frames)
• Adds Ruby markup
• Proposed recommendation review period ends: 7 May 2001

XHTML 1.1 Modules

Structure, Text, Hypertext, List, Object, Presentation, Edit, Bidirectional Text, Forms, Tables, Image, Client-side Image Map, Server-side Image Map, Intrinsic Events, Metainformation, Scripting, Stylesheet, Style Attribute (Deprecated ), Link, Base, Ruby.

Ruby

Example Ruby markup

<ruby>
  <rb>WWW</rb>
  <rp>(</rp><rt>World Wide Web</rt><rp>)</rp>
</ruby>

Use CSS to describe presentation

XHTML 2.0

XHTML 2.0 is still in preparation

• More generic XML
• New forms
• New events
• Fix frames
• Replace some need for scripting
• More accessibility
• First working draft: this summer

The problems with frames

• Can't bookmark framesets
• [Back] does odd things
• [Page up] and [page down] work oddly
• [Reload] often doesn't work right
• Security is compromised
• Nested frames are hard to deal with (how do you get out?)
• Search results
• <noframes>

What frames can do

• Search and show interfaces
• Keeping script variables in a hidden frame

Forms

• Being produced by a separate group
• Consists of three parts:
  • data model
  • instances
  • user interface
• Will include much more client-side checking
• Form data will be sent to the server as XML
• Separates content from presentation (e.g. a radio button and a select box both allow you to select one from many, and you may want to use different choices on different devices)

Events

• Current events are almost all in terms of mouse: onclick, onmouseover, onfocus, etc.
• Future event model will be device independent, and allow you to define your own new events
• Uses the DOM event model

The DOM

• Domain Object Model: how you access a document via scripting
• Currently only an XML DOM
• An XHTML DOM is being investigated

Accessibility problems

• A sighted person can work out the structure from the visual presentation
• A non-sighted person cannot: the structure must be present in the markup
• That is why new features were added to forms and tables in HTML 4, like <caption>
• Text would also benefit from such a treatment: not h1, h2 etc (which are subject to misuse) but nested sections with their own headings

Example of structure

    <section>
	<h>XHTML</h>
	...
	<section>
		<h>Structure</h>
		...
	</section>
    </section>

CSS can still handle it:

    section h { how an h1 should look }
    section section h { h2 }
    section section section h { h3 }

etc.

Roadmap

To Find Out More

• All XHTML developments are made public at www.w3.org/Markup/
• Forms at www.w3.org/Markup/Forms/
• Members of W3C can also look at www.w3.org/Markup/Group/ www.w3.org/Markup/Forms/Group/