XHTML

1
XHTML

• Presentation by Kevin See
• June 16, 2000

2
XML in HTML Meeting Report

• May 11, 1998
• http//www.oasis-open.org/cover/NOTE-xh-19980511.h
  tml
• How do we hide new idioms from deployed
  software
• How do we introduce new idioms with distinctive
  display characteristics, such as MathML?

3
What Is XHTML?

• XHTML (Extensible Hypertext Markup Language) is
  a reformulation of HTML 4 as an application of
  the Extensible Markup Language (XML)
• XHTML is a family of current and future document
  types and modules that reproduce, subset, and
  extend HTML 4.

4
Why Would You Want to Use XHTML?

• Extensibility
• Powerful machine
• New tags / attributes
• Lead to more complicated pages and larger programs

• Portability
• Small devices mobile devices and possibly
  household devices
• Several levels of possible markup
• Web pages can now be made simpler

5
Document Conformance

• Strictly conforming documents
• Must validate against proposed DTDs.
• Root element must be lthtmlgt.
• Root element must designate the XHTML namespace
  using the xmlns attribute. (see next slides for
  details)
• There must be a DOCTYPE declaration in the
  document prior to the root element.

6
Document Conformance- Using XHTML With Other
Namespaces

• lthtml xmlns"http//www.w3.org/1999/xhtml"
  xmllang"en" lang"en"gt
• ltheadgt
• lttitlegtA Math Examplelt/titlegt
• lt/headgt
• ltbodygt
• ltpgtThe following is MathML
  markuplt/pgt
• ltmath xmlns"http//www.w3.org/1
  998/Math/MathML"gt
• ltapplygt ltlog/gt
• ltlogbasegt
• ltcngt 3 lt/cngt
• lt/logbasegt
• ltcigt x lt/cigt
• lt/applygt
• lt/mathgt
• lt/bodygt
• lt/htmlgt

7
Document Conformance- Using XHTML With Other
Namespaces

• lt?xml version"1.0" encoding"UTF-8"?gt
• lt!-- initially, the default
  namespace is "books" --gt
• ltbook xmlns'urnloc.govbooks'
• xmlnsisbn'urnISBN0-395-36341
  -6' xmllang"en" lang"en"gt
• lttitlegtCheaper by the
  Dozenlt/titlegt
• ltisbnnumbergt1568491379lt/isbnnumb
  ergt
• ltnotesgt
• lt!-- make HTML the default
  namespace for a hypertext commentary --gt
• ltp xmlns'http//www.w3.org/1999
  /xhtml'gt
• This is also available lta
  href"http//www.w3.org/"gtonlinelt/agt.
• lt/pgt
• lt/notesgt
• lt/bookgt

8
User Agent Conformance

• http//www.w3.org/TR/xhtml1/
• Consistent with XML
• Consistent with facilities definition
• Recognize attributes of type ID
• Unrecognized Items
• Space, Tab, Carriage Return, Line Feed are
  considered as white space.

9
DTDs Document Type Definitions

• XHTML 1.0 specifies three XML document types that
  correspond to the three HTML 4.0 DTDs
• lt!DOCTYPE html PUBLIC
• "-//W3C//DTD XHTML 1.0 Strict//EN"
• "DTD/xhtml1-strict.dtd"gt ------
  XHTML 1.0 Strict
• lt!DOCTYPE html PUBLIC
• "-//W3C//DTD XHTML 1.0
  Transitional//EN"
• "DTD/xhtml1-transitional.dtd"gt
  ------ XHTML 1.0 Transitional
• lt!DOCTYPE html PUBLIC
• "-//W3C//DTD XHTML 1.0
  Frameset//EN"
• "DTD/xhtml1-frameset.dtd"gt ------
  XHTML 1.0 Frameset

10
Differences With HTML 4

• Document must be well-formed
• Tag and attribute names must be written in
  lower-case (see XHTML Case Poll)
• For non-empty elements, end tags are required
• Empty elements must be terminated (e.g. ltbr /gt )
• Attribute values must always be quoted (e.g. ltimg
  border 0 /gt
• Attribute value pairs cannot be minimized (e.g.
  ltul compact compact gt )
• name attribute is formally deprecated (to be
  removed later), use id attribute instead

11
Differences With HTML 4

• ltscriptgt and ltstylegt elements are declared as
  having PCDATA content.
• e.g.
• ltscript language"JavaScript type"text/javascrip
  t"gt
• lt!CDATA
• document.write("ltbgtHello
  World!lt/bgt")
• gt
• lt/scriptgt

12
Differences With HTML 4 SGML Exclusions

• a
• cannot contain other a elements.
• pre
• cannot contain the img, object, big, small, sub,
  or sup elements.
• button
• cannot contain the input, select, textarea,
  label, button, form, fieldset, iframe or isindex
  elements.
• label
• cannot contain other label elements.
• form
• cannot contain other form elements.

13
Compatibility Issues With Existing User Agent

• Although there is no requirement for XHTML 1.0
  documents to be compatible with existing user
  agents, in practice this is easy to accomplish.
• Appendix C summarizes design guidelines for
  authors who wish their XHTML documents to render
  on existing HTML user agents. http//www.w3.org/TR
  /xhtml1/

14
XHTML Document Structure

• An XHTML document consists of three main parts
• The DOCTYPE, The Head, and The Body
• Here is a minimal XHTML document
• 1 lt!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
  Transitional//EN "DTD/xhtml1-transitional.dtd"gt
• 2 lthtml xmlns"http//www.w3.org/1999/xhtml"gt
• 3 ltheadgt
• 4 lttitlegtMinimal documentlt/titlegt
• 5 lt/headgt
• 6 ltbodygt
• 7 ltpgt
• 8 lta href"http//validator.w3.org/check/ref
  erer"gt validatelt/agt
• 9 lt/pgt
• 10lt/bodygt
• 11lt/htmlgt

15
Future Directions

• Modularizing XHTML (hand held device) The
  process of modularization breaks up XHTML up into
  a series of smaller element sets. These elements
  can then be recombined to meet the needs of
  different communities.

16
Future Directions

• Document Profiles
• A document profile specifies the syntax and
  semantics of a set of documents.
• Conformance to a document profile provides a
  basis for interoperability guarantees.
• The document profile specifies the
  facilities required to process documents of that
  type.

17
Conclusion

• Example of site written in XHTML - Brian White
  Associates
• XHTML 1.0 Combines the Familiarity of HTML with
  the Power of XML
• XHTML 1.0 Provides a Foundation for
  Device-Independent Web Access
• XHTML 1.0 allows authors to create Web documents
  that work with current HTML browsers and that may
  be processed by XML- enabled software as well.
• With XHTML, we are well-prepared to move into the
  21st century web.

18
Interesting URLs

• HTML conversion tool Tidy
• HTML Writers Guild world largest international
  organization of web authors (over 110,000
  members, over 150 countries)
• W3C HTML validation Service
• HTML Validator Commercial Product
• FOP formatter that produces PDF from XSL
  formatting objects

19
Interesting URLs

• W3C's Amaya Browser - The latest release includes
  the support of HTML 4.0 and XHTML
• Slide set on XHTML -This is a recent slide set
  for XHTML first presented at the W3LA
  event in Stockholm on 24th March 1999.