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Tutorial 9
1
Working with XHTML
XPSGML
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Standard Generalized Markup Language (SGML) A standard for specifying markup languages.Large, complex standard capable of specifying many
different types of markup languages.Device and System Independent
MML: Math Markup Language is a markup language:
Rendering
Code
XPSGML HTMLSGML XML XHTML
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SGML RULES
HTML
XML RULES
XHTMLInconsistent, browser support difficult
Consistent rules for efficient browser support
Many other markup
languages
Other XML languages
XP
HTML and XHTML
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HTML (Hypertext Markup Language)1998: Version 4.0 most current (4.01 not officially
implemented)Can be applied inconsistentlyBrowser code must be complex, inefficient, to
handle inconsistencies.
XHTML (Extensible Hypertext Markup Language)2002: Version 1.1 most current (1.0 still extensively
used)Strict standards for consistency.Browser code can be efficient, run on small devices.
XP
XHTML Versions
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XPAbout XHTML Documents1. An XHTML document that correctly follows the
syntax rules is called a well-formed document.
2. Because XHTML documents conform to XML rules, enter an “XML declaration” (XML Prolog) as the first line of the file.
3. A special document called a “DTD” (document type definition) is used to specify correct content and structure.
4. A special attribute called the “xhtml namespace” is inserted in the opening <html> tag.
5. If the document is well-formed and also has correct content and structure, it is called a valid document.6
XPAn XHTML document that correctly follows the syntax rules is called a well-formed document.
7 “attribute minimization” not allowed
XPBecause XHTML documents conform to XML rules, enter an “XML declaration” (XML Prolog) as the first line of the file.
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For XHTML documents, use the declaration:
<?xml version=“1.0” encoding=“UTF-8”?>
XML Version number
character encoding
XPA special document called a “DTD” (document type definition) is used to specify correct content and structure.
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• The DOCTYPE declaration, which tells which DTD is associated with the document, is the second line of the file, after the XML prolog statement. It is used to tell the browser what version of the markup language the page is written in.
<!DOCTYPE root type “id” “url”>
XPDocument Type Definition (“DTD”)
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- The DTD specifies the rules for a valid document
- There are 3 types of the XHTML DTD- Transitional: allows many of the older HTML
features but not framesets- Frameset: allows many of the older HTML
features including framesets- Strict: does not allow any presentational features
or deprecated HTML elements and attributes. Does not support frames or inline frames. Used when there is a need to strictly conform to the latest standards
- There are also definitions for straight HTML documents.dtd_list.txt This link can also be found on my Data for Labs page
XPDocument Elements that are not valid under the Strict DTD
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Elements not allowed under the strict DTD are:
appletbasefontcenterdirfontframeframeset
iframeisindexmenunoframessstrikeu
http://www.w3schools.com/tags/tag_dir.asp List and description of all tags
XPAttributes under the Strict DTD
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Some attributes are restricted, while others are required in XHTML
Restricted (prohibited) attributes under the strict XHTML DTD are shown on page 536 of the textbook.
Required attributes under the strict XHTML DTD are shown on page 537 of the textbook.
XPAttributes Prohibited under the Strict DTD
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XPAttributes Required under the Strict DTD
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XPA special attribute called the “xhtml namespace” is inserted in the opening <html> tag.
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• To set XHTML as the default namespace for a document, add the xmlns attribute to the html element with the following value:
<html xmlns=“http://www.w3.org/1999/xhtml”>
• A namespace is any string of characters that uniquely identifies the set of elements and attributes belonging to the particular language.
dtd_list.txt This link can also be found on my Data for Labs page
XPIf the document is well-formed and also has correct content and structure, it is called a valid document
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This is an example of an xhtml document that correctly conforms to the “Strict” DTD
XHTML can be checked for validation at http://validator.w3.org
XPValidation of XHTML
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Click “Validate by File Upload”Click “Browse”
XPValidation of XHTML
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Select the file you want to validateClick “Check”
XPValidation of XHTML
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If it is valid, you get “…successfully checked. . .”
XPValidation of XHTML
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This is an example of an xhtml document that does not conform to the “Strict” DTD
(Can you see the error?)
XPValidation of XHTML
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If it is not valid you get “Error found . . . “
“bgcolor” is not allowed under the strict DTD
http://validator.w3.org
XPValidation of XHTML
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To validate under a different version of the DTD, change the DOCTYPE declaration
XPUsing Style Sheets and XHTML
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• Style sheets sometimes contain characters that could cause problems for the browser:
• A CDATA section marks a block of text so that the browser will not treat text as html code:
> means any img element that is a direct descendent of a p element.
• If your code contains characters like > , it’s best to use an external style sheet instead of an embedded one.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Convert body element attributes to styles in a style sheet.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Correct errors for one or two-sided elements not properly closed or one-sided tags not terminated.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Use the float style to align inline images.
180-img-styles.htm
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Remove/replace deprecated elements or attributes.
185-img-styles.htm
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Remove/replace deprecated elements or attributes.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Remove/replace deprecated elements or attributes.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Replace formatting done with <b> and or <font> by styles.
XPFixing XHTML Validation Errors
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• Some examples of things you might need to do to make an xhtml file pass the validator check:
Replace prohibited
attributes such as name with a valid attribute such as
id
XPThe End
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