XML became a W3C recommendation in 1998. It is a subset of SGML that describes data objects called XML documents using tags that are not predefined. The goal of XML was to enable generic SGML to be served, received, and processed on the web in a way that was not possible with HTML by creating compulsory rules. XML documents consist of characters from Unicode and are divided into markup and content. They begin with an XML declaration and document type declaration and contain elements enclosing data content and attributes. Schemas and DTDs define elements, attributes, and structure for XML documents. Stylesheets like CSS and XSLT can transform XML into HTML for browser viewing. Current browsers support XML with associated stylesheets.

1. XML
By Elizabeth Wiley

2. eXtensible Markup Language
 Became a W3C recommendation in 1998
 Subset of SGML (Standard Generalized Markup
Language)
 Describes a class of data objects called XML documents
 Metalanguage (language for describing other
languages)
 Tags are not predefined, designed to be self-prescriptive
“XML is a software- and hardware-dependent tool for
carrying information.”4

3. The goal of XML: Why?
To enable generic SGML to be  Browsers never allowed
served, received, and SGML
processed on the Web in a
way that is not possible with  HTML is easy to corrupt or
break
HTML. XML has been designed
to operate with both SGML  Widespread
and HTML.  Held back
development
 XML fixes that by creating
compulsory rules

4. The Basics
 XML documents consist entirely of characters from
Unicode (not all Unicode characters are included).
 Characters that make up XML are divided into markup
and content.
 Unicode character sets are encoded into bytes for
storage or transmission.
 The processor analyses the markup and passes structured
information to an application.

5. XML Document
 Begins with XML declaration and document type
declaration
 Followed by Document Instance, containing root
element (start/end tags) and elements enclosing the
data content (text) and any attributes („name=“value”‟
pairs)
 Documents can be simple, with straightforward nested
markup, or more complicated with Schema or DTD
(describe structure of the document)

6. Schema and DTD (Document Type Definition)
 Define the allowed parts of an XML document:
 The elements and attributes that can appear
 Data types, default and fixed values
 Identify child elements, and their order and number
 Whether an element is empty or includes text
 Schemas are the successors of DTDs
 Extensible to future additions, richer and more
powerful, support data types and namespaces, written in
XML
 XML Schema became a W3C recommendation in 2001

7. Stylesheets (CSS and XMLT)
 Transform XML into HTML
 Allow for document management benefits of XML, but
readers don‟t need XML smarts in their browsers
 XMLT is an document processing language that uses XML
source code
 Declares rules for processor to use when interpreting XML
document

8. Browsers
Current versions of Internet Explorer, Firefox, Safari,
Chrome, and Opera all support XML with CSS or
XSLT stylesheets.
Does not work with any versions of Netscape, IE
6.0 or earlier, or early versions of Mozilla.

9. The Difference
XML HMTL
 Designed to transport and  Designed to display data
store data
 Focuses on how data looks
 Focuses on what data is
XHTML is “a reformulation of HTML 4 in XML
1.0”

10. HTML5
 Intended to include HTML and XHTML
 XHTML5 is an XML serialization of HTML5, meaning the
data structure or object state is converted into a form
that can be stored.

11. Sources
1 http://xml.silmaril.ie/
2 http://xml.coverpages.org/xml.html
3 http://en.wikipedia.org/wiki/XML
4 http://www.w3schools.com/xml/xml_whatis.asp
5 http://www.w3schools.com/Schema/schema_intro.asp
6 http://en.wikipedia.org/wiki/Serialization
7 http://en.wikipedia.org/wiki/HTML5#XHTML5