xhtml presentation by kevin see june 16, 2000. xml in html meeting report may 11, 1998 ...
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XHTML
Presentation by Kevin See
June 16, 2000
XML in HTML Meeting Report
May 11, 1998 http://www.oasis-open.org/cover/NOTE-xh-
19980511.html How do we “hide” new idioms from
deployed software How do we introduce new idioms with
distinctive display characteristics, such as MathML?
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.
Why Would You Want to Use XHTML?Extensibility
1. Powerful machine
2. New tags / attributes
3. Lead to more complicated pages and larger programs
Portability
1. Small devices – mobile devices and possibly household devices
2. Several levels of possible markup
3. Web pages can now be made simpler
Document Conformance
Strictly conforming documents Must validate against proposed DTDs. Root element must be <html>. 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.
Document Conformance- Using XHTML With Other Namespaces
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>A Math Example</title> </head> <body> <p>The following is MathML markup:</p> <math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <log/> <logbase> <cn> 3 </cn> </logbase> <ci> x </ci> </apply> </math> </body> </html>
Document Conformance- Using XHTML With Other Namespaces
<?xml version="1.0" encoding="UTF-8"?>
<!-- initially, the default namespace is "books" -->
<book xmlns='urn:loc.gov:books'
xmlns:isbn='urn:ISBN:0-395-36341-6' xml:lang="en" lang="en">
<title>Cheaper by the Dozen</title>
<isbn:number>1568491379</isbn:number>
<notes>
<!-- make HTML the default namespace for a hypertext commentary -->
<p xmlns='http://www.w3.org/1999/xhtml'>
This is also available <a href="http://www.w3.org/">online</a>.
</p>
</notes>
</book>
User Agent Conformance
http://www.w3.org/TR/xhtml1/
1. Consistent with XML
2. Consistent with facilities definition
3. Recognize attributes of type ID
4. Unrecognized Items
5. Space, Tab, Carriage Return, Line Feed are considered as white space.
DTDs – Document Type Definitions XHTML 1.0 specifies three XML document types that
correspond to the three HTML 4.0 DTDs: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd"> ------ XHTML 1.0 Strict
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "DTD/xhtml1-transitional.dtd"> ------ XHTML 1.0 Transitional
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "DTD/xhtml1-frameset.dtd"> ------ XHTML 1.0 Frameset
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. <br /> ) Attribute values must always be quoted (e.g. <img …
border = “0” /> Attribute value pairs cannot be minimized (e.g. <ul
compact = “compact” > ) “name” attribute is formally deprecated (to be removed
later), use “id” attribute instead
Differences With HTML 4 <script> and <style> elements are declared as having
#PCDATA content.
e.g.
<script language="JavaScript type="text/javascript">
<![CDATA[
document.write("<b>Hello World!</b>");
]]>
</script>
Differences With HTML 4 – SGML Exclusionsa
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.
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/
XHTML Document StructureAn XHTML document consists of three main parts: The DOCTYPE, The Head, and The BodyHere is a minimal XHTML document1: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN“ "DTD/xhtml1-transitional.dtd">2: <html xmlns="http://www.w3.org/1999/xhtml">3: <head>4: <title>Minimal document</title>5: </head>6: <body>7: <p>8: <a href="http://validator.w3.org/check/referer"> validate</a>9: </p>10:</body>11:</html>
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.
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.
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.
Interesting URLs
HTML conversion tool – Tidy HTML Writers Guild – world largest intern
ational 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
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.