What is XML?

Extensible Markup Language XML 1.0 1998
Easier-to-use subset of SGML (Standard Generalized Markup Language)
XML is a text-based markup language
Standard for data interchange on the web
Set of rules for designing semantic tags
Meta-markup language to define other languages
XML 1.0 Specification
http://www.w3.org/TR/REC-xml

HTML and XML

HTML is an application of SGML
XML is a subset of SGML
XHTML is an application of XML

XML File Sample

   <?xml version="1.0"?>
   <dining-room>
      <manufacturer>The Wood Shop</manufacturer>
      <table type="round" wood="maple">
         <price>$199.99</price>
      </table>
      <chair wood="maple">
         <quantity>6</quantity>
         <price>$39.99</price>
      </chair>
   </dining-room>

XML describes Structure and Semantics, Not Formatting

HTML Example

   <DL>
   <DT>Mambo
   <DD>by Enrique Garcia
   </DL>
   <UL>
   <LI>Producer: Enrique Garcia
   <LI>Publisher: Sony Music Entertainment
   <LI>Length: 3:46
   <LI>Written: 1991
   <LI>Artist: Azucar Moreno
   </UL>

XML describes Structure and Semantics, Not Formatting (2)

XML Example

   <SONG>
      <TITLE>Mambo</TITLE>
      <COMPOSER>Enrique Garcia</COMPOSER>
      <PRODUCER>Enrique Garcia</PRODUCER>
      <PUBLISHER>Sony Music Entertainment</PUBLISHER>
      <LENGTH>3:46</LENGTH>
      <YEAR>1991</YEAR>
      <ARTIST>Azucar Moreno</ARTIST>
   </SONG>

What's So Great About XML?

Easy Data Exchange

Growth of propietary data formats
Conversion Programs (Applications, versions ..)
Data and markup are stored as text
Avoid store simple data in huge files

What's So Great About XML? (2)

Customizing Markup Languages

Banking Industry Technology Secretariat (BITS)
Financial Exchange (IFX)
Schools Interoperability Framework (SIF)
Common Business Library (CBL)
Electronic Business XML Initiative (ebXML)
The Text Encoding Initiative (TEI)

What's So Great About XML? (3)

Self-Describing Data

   <?xml version="1.0" encoding="UTF-8"?>
   <DOCUMENT>
      <GREETING>Hello from XML</GREETING>
      <MESSAGE>Welcome to Programing XML in Java</MESSAGE>
   </DOCUMENT>

What's So Great About XML? (4)

Structured and Integrated Data

   <?xml version="1.0"?>
   <SCHOOL>
      <CLASS type="seminar">
         <CLASS_TITLE>XML In The Real World</CLASS_TITLE>
         <CLASS_NUMBER>6.031</CLASS_NUMBER>
         <SUBJECT>XML</SUBJECT>
         <START_DATE>6/1/2002</START_DATE>
         <STUDENTS>
            <STUDENT status="attending">
               <FIRST_NAME>Edward</FIRST_NAME>
               <LAST_NAME>Samson</LAST_NAME>
            </STUDENT>
            <STUDENT status="withdrawn">
               <FIRST_NAME>Ernestine</FIRST_NAME>
               <LAST_NAME>Johnson</LAST_NAME>
            </STUDENT>
         </STUDENTS>
      </CLASS>
   </SCHOOL>

Well-Formed XML Documents

Follow the syntax rules setup for XML by W3C in
The XML 1.0 Specification (www.w3.org/TR/REC-xml)
Contain one or more elements
Root element must contain all the other elements
Each element nest inside any enclosing elements properly

Valid XML Documents

Association with a Document Type Definition (DTD)
Comply with that DTD

     <?xml version="1.0" encoding="UTF-8"?> 
     <?xml-stylesheet type="text/css" href="first.css"?>
     <!DOCTYPE DOCUMENT [                  
        <!ELEMENT DOCUMENT (GREETING, MESSAGE)>                  
        <!ELEMENT GREETING (#PCDATA)>
        <!ELEMENT MESSAGE (#PCDATA)>
     ]>

     <DOCUMENT>
        <GREETING>Hello from XML</GREETING>
        <MESSAGE>Welcome to Programing XML in Java</MESSAGE>
     </DOCUMENT>

Related Technologies

Hypertext Markup Language

HTML most common output format of XML
Web Browsers: Internet Explorer 5.0, Netscape 6.0
Different way to design a Web site.

Related Technologies (2)

Cascading Style Sheets

Define formatting properties

Font Size
Font family
Font weight
Paragraph indentation
Paragraph alignment

Multiple style sheets can be applied to a single document
Multiple styles can be applied to a single element.

Related Technologies (3)

URLs and URIs

Uniform Resource Locator (URL)
http://www.cs.rpi.edu/~puninj/XMLJ/
Uniform Resource Name (URN)
urn:issn:1082-9873
http://purl.oclc.org/OCLC/PURL/FAQ
Uniform Resource Identifier (URI)

Related Technologies (4)

The Unicode Character Set

American Standard Code for Information Interchange (ASCII) 0-255 'A' - 65
XML provides full Support for the two-byte Unicode Character Set. 0-65,535
http://www.unicode.org
XML Documents written in:

ASCII
UTF-8 Compressed version of Unicode (uses 8 bits to represent characters)
<?xml version="1.0" encoding="UTF-8"?>

XML defines character reference to encode Unicode characters.
© < π
Universal Character System (UCS ISO 10646)

4 bytes per symbol
UCS-2 and UCS-4 encoding

How Do I Use XML?

XML Document is parsed
Data is manipulated
APIs available in Java, C, C++, Perl..

Simple API for XML - SAX

Event-based framework for parsing XML data
Methods such as startDocument(), endElement()
Set of errors and warnings
http://www.megginson.com/SAX
Several parsers can be plugged into the SAX API

Document Object Model - DOM

Manipulation of XML Data
Provides a representation of an XML Document as a tree.
Reads XML Document into memory
http://www.w3.org/DOM

Sun's Java API for XML Parsing - JAXP

Provide cohesiveness to the SAX and DOM APIs
Add convenient methods for Java developers
http://java.sun.com/xml

Java and XML: A Perfect Match

Java is portable code, XML is portable data
Applications completely portable

Java Virtual Machine (JVM)
Standards-based data layer

Java provides the most robust set of:

APIs - JAXP
Parsers - XP
Processors - Saxon
Publishing Frameworks - Cocoon
Tools for XML - XML Pro

The Life of an XML Document

XML Editors

Create XML documents

Text Editors - vi, emacs, notepad
XML Editors

Adobe FrameMaker, www.adobe.com
XML Pro, www.vervet.com
XML Writer, xmlwriter.net
XML Notepad, msdn.microsoft.com/xml/notepad/intro.asp
XMetal from SoftQuad, xmetal.com
XML Spy, www.xmlspy.com

XML Editors (XML Spy)

More XML Spy

XML Parsers

Read XML Document
Verify that XML is well formed
Verify that XML is valid

expat, parser written in C by James Clark (www.jclark.com)
XML for Java (XML4J), from IBM Alphaworks
(www.alphawors.ibm.com/tech/xml4j)
Lark, written in Java (www.textuality.com/Lark/)
Apache Xerces (www.apache.org)
XP by James Clark (www.jclark.com)
Oracle XML Parser (technet.oracle.com/tech/xml)
Sun Microsystems Project X (java.sun.com/products/xml)

XML Validators

Verify that XML is valid

XML.com's Validator based on Lark (xml.com)
Language Technology Group at the University of Edinburgh's validator based on the RXP Parser
www.ltg.ed.ac.uk/~richard/xml-check.html
Scholarly Technology Group at Brown University's validator
www.stg.brown.edu/service/xmlvalid/

XML Browsers

Display the Data to the User

Internet Explorer 5

Display directly XML Documents
Handle XML in scripting Languages (JScript, VBScript)
Bind XML to ActiveX Data Object (ADO) database recordsets
XML integrated into the Office 2000 suite of applications

Netscape Navigator 6

Display directly XML Documents
Handle XML in scripting Languages (Javascript 1.5)
Support the XML-based User Interface Language (XUL). XUL lets you configure the controls in the browser

Jumbo

Display XML
Use CML to draw molecules

XML Resources

XML at W3C (http://www.w3.org/xml/)
XML.com (http://www.xml.com/
XML.org Registry (http://www.xml.org/)
XML Cover Pages (http://xml.coverpages.org/)
Java and XML (http://java.sun.com/xml/)

XML Applications

Languages based on XML

Chemical Markup Language (CML)
Mathematical Markup Language (MathML)
Channel Definition Format (CDF)
Synchronized Multimedia Integration Language (SMIL)
XHTML
Scalable Vector Graphics (SVG)
MusicML
VoxML