Introduction to XML

eXtensible Markup Language (XML)
By:
Abhra Basak
Shoubhik Debnath

Journey Ahead…….
• Introduction
• Comparison between XML and HTML
• XML Syntax
• XML Elements v/s Attributes
• XML Data Islands
• DocumentType Definition
• XML Query Languages
• Converting Relational Database to XML
• XMLTechnologies
• Role of XML inWBIM

What is XML?
• eXtensible Markup Language
• Markup languages are for documents containing
structured information.
• Markup languages are designed for the processing,
definition and presentation of text
• Defined by four specifications:
• XML, the Extensible Markup Language
• XLL, the Extensible Linking Language
• XSL, the Extensible Style Language
• XUA, the XML User Agent

XML….
• Based on Standard Generalized Markup Language (SGML)
• Version 1.0 introduced byWorldWide Web Consortium
(W3C) in 1998
• Bridge for data exchange on
theWeb

Why eXtensible ?
• Introducing Dynamic nature.
• Approaches to extensibility include facilities (sometimes called hooks) for
allowing users to insert their own program routines, the ability to define
new data types, and the ability to define new formatting markup tags.

Difference Between XML and
HTML
• XML is not a replacement for HTML.
• XML and HTML were designed with different goals:
1. XML was designed to transport and store
data, with focus on what data is
2. HTML was designed to display data, with
focus on how data looks
• HTML is about displaying information, while XML is about
carrying information.

Comparisons
• Extensible set of tags
• Content orientated
• Standard Data infrastructure
• Fixed set of tags
• Presentation oriented
• No data validation capabilities
XML HTML

XML Documents Form aTree
Structure
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
</book>
<book category="WEB">
<title lang="en">LearningXML</title>
<author>ErikT. Ray</author>
<year>2003</year>
</book>
</bookstore>

XML Syntax Rules
1. All XML Elements Must Have a ClosingTag
• Legal Statement:
<p>This is a paragraph.</p>
<br />

XML Syntax Rules
2. XMLTags are Case Sensitive
<Message>This is incorrect</message>
<message>This is correct</message>

XML Syntax Rules
3. XML Elements Must be Properly Nested
<b><i>This text is bold and italic</i></b>

XML Syntax Rules
4. XML Documents Must Have a Root Element
<root>
<child>
<subchild>.....</subchild>
</child>
</root>

XML Syntax Rules
5. XML AttributeValues Must be Quoted
<note date="12/11/2007">
<to>Tove</to>
<from>Jani</from>
</note>

XML Syntax Rules
6. Comments in XML
The syntax for writing comments in XML is similar to that of HTML.

XML Syntax Rules
7. Entity References : Some characters have a special meaning in XML.
< < less than
> > greater than
& & ampersand
' ' apostrophe
" " quotation mark

Authoring XML Elements
• An XML element is made up of a start tag, an end tag, and data
in between.
• Example:
<director> Matthew Dunn </director>
• Example of another element with the same value:
<actor> Matthew Dunn </actor>
• XML tags are case-sensitive:
<CITY> <City> <city>
• XML can abbreviate empty elements, for example:
<married> </married> can be abbreviated to
<married/>

Authoring XML Elements
(cont’d)
• An attribute is a name-value pair separated by an equal
sign (=).
• Example:
<City ZIP=“94608”> Emeryville </City>
• Attributes are used to attach additional, secondary
information to an element.

XML Elements vs.
Attributes
<person sex="female">
<firstname>Anna</firstname>
<lastname>Smith</lastname>
</person>
sex is an ATTRIBUTE
<person>
<sex>female</sex>
<firstname>Anna</firstname>
<lastname>Smith</lastname>
</person>
sex is an ELEMENT

XML Data Model: Example
<BOOKS>
<book id=“123” loc=“library”>
<author>Hull</author>
<title>California</title>
<year> 1995 </year>
</book>
<article id=“555” ref=“123”>
<author>Su</author>
<title> Purdue</title>
</article>
</BOOKS> Hull Purdue
BOOKS
123 555
California
Su
titleauthor
title
author
article
book
year
1995
ref
loc=“library”

Authoring XML Data Islands
• A data island is an XML document that exists within an
HTML page.
• The <XML> element marks the beginning of the data
island, and its ID attribute provides a name that you can
use to reference the data island.

Authoring XML Data Islands
(cont’d)
• Example:
<XML ID=“XMLID”>
<customer>
<name> Mark Hanson </name>
<custID> 29085 </custID>
</customer>
</XML>

DocumentType Definitions
(DTD)
• An XML document may have an optional DTD.
• DTD serves as grammar for the underlying XML
document, and it is part of XML language.
• DTDs are somewhat unsatisfactory, but no consensus
exists so far beyond the basic DTDs.
• DTD has the form:
<!DOCTYPE name [markupdeclaration]>

DTD (cont’d)
• Consider an XML document:
<db><person><name>Alan</name>
<age>42</age>
<email>agb@usa.net </email>
</person>
<person>………</person>
……….
</db>

DTD (cont’d)
• DTD for it might be:
<!DOCTYPE db [
<!ELEMENT db (person*)>
<!ELEMENT person (name, age, email)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
<!ELEMENT email (#PCDATA)>
]>

XML Query Languages
• The first XML query languages
• LOREL (Stanford)
• XQL
• Several other query languages have been developed (e.g.
UNQL, XPath)
• XML-QL considered byW3C for standardization
• CurrentlyW3C is considering and working on a new query
language: XQuery

A Query Language for
XML: XML-QL
• Developed at AT&T labs
• To extract data from the input XML data
• Has variables to which data is bound and templates which
show how the output XML data is to be constructed
• Uses the XML syntax
• Based on a where/construct syntax
• Where combines from and where parts of SQL
• Construct corresponds to SQL’s select

XML-QL Query: Example 1
• Retrieve all authors of books published by Morgan Kaufmann:
where <book>
<publisher><name>
Morgan Kaufmann
</name> </publisher>
<title> $T </title>
<author> $A </author>
</book> in “www.a.b.c/bib.xml”
construct <result> $A </result>

XML-QL Query: Example 2
• XML-QL query asking for all bookstores that sell TheJava
Programming Language for under $25:
where <store>
<name> $N </name>
<book>
<title>The Java Programming Language </title>
<price> $P </price>
</book>
</store> in “www.store/bib.xml”
$P < 25
construct <result> $N </result>

Converting Relational Database to XML
Example: Export the following data into XML and group books by
store
• Relational Database:
Store (sid, name, phone)
Book (bid, title, authors)
StoreBook (sid , bid, price, stock)
Store BookStoreBook
phone
authors
bidtitlesid
name
price stock

Converting Relational Database to
XML (Cont’d)
• XML:
<store> <name> … </name>
<phone> … </phone>
<book> <title>… </title>
<authors> … </authors>
<price> … </price>
</book>
<book>…</book>
…
</store>

XMLTechnologies
• XHTML (Extensible HTML) :A stricter and cleaner XML based version of
HTML.
• XML DOM (XML Document Object Model) : A standard document model for
accessing and manipulatingXML.
• XSL (Extensible Style Sheet Language) XSL consists of three parts:
1. XSLT (XSLTransform) - transforms XML into other formats, like HTML
2. XSL-FO (XSL Formatting Objects)- for formatting XML to screen, paper, etc
3. XPath - a language for navigatingXML documents
• XQuery (XML Query Language) :An XML based language for querying XML
data.
• DTD (DocumentType Definition) :A standard for defining the legal elements
in an XML document.

Role of XML inWBIM
• XML is very easy to understand.
• An efficient method for Information Storage and Retrieval – Its simple
syntax enables that unlike RDBMS.
• There are obviously some security concerns. So, future work on XML
Security is promising.

THANKYOU
Comments and Questions
are most welcome!

Introduction to XML

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