Introduction to XML

Department of Information Technology 1Data base Technologies (ITB4201)
Introduction to XML
Dr. C.V. Suresh Babu
Professor
Department of IT
Hindustan Institute of Science & Technology

Action Plan
 What is XML?
 Syntax of XML Document
 DTD (Document Type Definition)
 XML Query Language
 XML Databases
 XML Schema
 Oracle JDBC
 Quiz

Introduction to XML
 XML stands for EXtensible Markup Language
 XML was designed to describe data.
 XML tags are not predefined unlike HTML
 XML DTD and XML Schema define rules to describe data
 XML example of semi structured data

The Difference Between XML and HTML
XML and HTML were designed with different goals:
• XML was designed to carry data - with focus on what data is
• HTML was designed to display data - with focus on how data
looks
• XML tags are not predefined like HTML tags are
4

XML Does Not Use Predefined Tags
• The XML language has no predefined tags.
• The tags in the example above (like <to> and <from>) are not
defined in any XML standard. These tags are "invented" by the
author of the XML document.
• HTML works with predefined tags like <p>, <h1>, <table>, etc.
• With XML, the author must define both the tags and the
document structure.
5

Building Blocks of XML
• Elements (Tags) are the primary components of XML
documents.
<AUTHOR id = 123>
<FNAME> JAMES</FNAME>
<LNAME> RUSSEL</LNAME>
</AUTHOR>
<!- I am comment ->
Element FNAME nested inside
element Author.
 Attributes provide additional information about Elements.
Values of the Attributes are set inside the Elements
Element Author
with Attr id
 Comments stats with <!- and end with ->

XML DTD (Document Type Definition)
 A DTD is a set of rules that allow us to specify our own set of
elements and attributes.
 DTD is grammar to indicate what tags are legal in XML
documents.
 XML Document is valid if it has an attached DTD and
document is structured according to rules defined in DTD.

DTD Example
<BOOKLIST>
<BOOK GENRE = “Science”
FORMAT = “Hardcover”>
<AUTHOR>
<FIRSTNAME> RICHRD
</FIRSTNAME>
<LASTNAME> KARTER
</LASTNAME>
</AUTHOR>
</BOOK>
</BOOKS>
<!DOCTYPE BOOKLIST[
<!ELEMENT BOOKLIST(BOOK)*>
<!ELEMENT BOOK(AUTHOR)>
<!ELEMENT
AUTHOR(FIRSTNAME,LASTNAM
E)>
<!ELEMENT
FIRSTNAME(#PCDATA)>
<!ELEMENT>LASTNAME(#PCDATA)
>
<!ATTLIST BOOK GENRE
(Science|Fiction)#REQUIRED>
<!ATTLIST BOOK FORMAT
(Paperback|Hardcover)
“PaperBack”>]>
Xml Document And
Corresponding DTD

XML Schema
 Serves same purpose as database schema
 Schemas are written in XML
 Set of pre-defined simple types (such as string, integer)
 Allows creation of user-defined complex types

XML Schema
• RDBMS Schema (s_id integer, s_name string, s_status string)
<Students>
<Student id=“p1”>
<Name>Allan</Name>
<Age>62</Age>
<Email>allan@abc.com
</Email>
</Student>
</Students>
 XMLSchema
<xs:schema>
<xs:complexType name = “StudnetType”>
<xs:attribute name=“id” type=“xs:string” />
<xs:element name=“Name” type=“xs:string />
<xs:element name=“Age” type=“xs:integer” />
<xs:element name=“Email” type=“xs:string” />
</xs:complexType>
<xs:element name=“Student”
type=“StudentType” />
</xs:schema>XML Document and Schema

XML Query Languages
• Requirement
Same functionality as database query languages (such as SQL)
to process Web data
• Advantages
• Query selective portions of the document (no need to
transport entire document)
• Smaller data size mean lesser communication cost

XQuery
• XQuery to XML is same as SQL to RDBMS
• Most databases supports XQuery
• XQuery is built on XPath operators
(XPath is a language that defines path expressions to locate
document data)

XPath Example
<Student id=“s1”>
<Name>John</Name>
<Age>22</Age>
<Email>jhn@xyz.com</Email>
</Student>
XPath: /Student[Name=“John”]/Email
Extracts: <Email> element with value “jhn@xyz.com”

Oracle and XML
• XML Support in Oracle
XDK (XML Developer Kit)
XML Parser for PL/SQL
XPath
XSLT

Oracle and XML
• XML documents are stored as XML Type ( data type for
XML ) in Oracle
 Internally CLOB is used to store XML
 To store XML in database create table with one
XMLType column
 Each row will contain one of XML records from XML
document
 Database Table: XML Document
 Database Row : XML Record

Examples
<Patients>
<Patient id=“p1”>
<Name>John</Name>
<Address>
<Street>120 Northwestern Ave</Street>
</Address>
</Patient>
<Patient id=“p2”>
<Name>Paul</Name>
<Address>
<Street>120 N. Salisbury</Street>
</Address>
</Patient>
</Patients>

Example
• Create table prTable(patientRecord XMLType);
• DECLARE
• prXML CLOB;
• BEGIN
• -- Store Patient Record XML in the CLOB variable
• prXML := '<Patient id=“p1">
• <Name>John</Name>
• <Address>
• <Street>120 Northwestern Ave</Street>
• </Address>
• </Patient>‘ ;
• -- Now Insert this Patient Record XML into an XMLType column
• INSERT INTO prTable (patientRecord) VALUES (XMLTYPE(prXML));
• END;

Example
TO PRINT PATIENT ID of ALL PATIENTS
SELECT
EXTRACT(p.patientRecord,
'/Patient/@id').getStringVal()
FROM prTable p;
USE XPATH

Oracle JDBC
 JDBC an API used for database connectivity
 Creates Portable Applications
 Basic Steps to develop JDBC Application
 Import JDBC classes (java.sql.*).
 Load JDBC drivers
 Connect and Interact with database
 Disconnect from database

Oracle JDBC
• DriverManager provides basic services to manage set of JDBC
drivers
 Connection object sends queries to database server after a
connection is set up
 JDBC provides following three classes for sending SQL statements
to server
 Statement SQL statements without parameters
 PreparedStatement SQL statements to be executed multiple times with different
parameters
 CallableStatement Used for stored procedures

Oracle JDBC
• SQL query can be executed using any of the objects.
(Statement,PreparedStatement,CallableStatement)
 Syntax (Statement Object )
Public abstract ResultSet executeQuery(String sql) throws SQLException
 Syntax (PreparedStatement,CallableStatement Object )
Public abstract ResultSet executeQuery() throws SQLException
 Method executes SQL statement that returns ResultSet object
(ResultSet maintains cursor pointing to its current row of data. )

XML Simplifies Things
• It simplifies data sharing
• It simplifies data transport
• It simplifies platform changes
• It simplifies data availability

Summary
• Many computer systems contain data in incompatible formats. Exchanging data
between incompatible systems (or upgraded systems) is a time-consuming task
for web developers. Large amounts of data must be converted, and incompatible
data is often lost.
• XML stores data in plain text format. This provides a software- and hardware-
independent way of storing, transporting, and sharing data.
• XML also makes it easier to expand or upgrade to new operating systems, new
applications, or new browsers, without losing data.
• With XML, data can be available to all kinds of "reading machines" like people,
computers, voice machines, news feeds, etc.

Test Yourself
1. What does XML stand for?
A. eXtra Modern Link B. eXtensible Markup Language
C. Example Markup Language D. X-Markup Language
2. Which statement is true?
A. All the statements are true B. All XML elements must have a closing tag
C. All XML elements must be lower case D. All XML documents must have a DTD
3. What does DTD stand for?
A. Direct Type Definition B. Document Type Definition
C. Do The Dance D. Dynamic Type Definition
4. Disadvantages of DTD are
(i)DTDs are not extensible
(ii)DTDs are not in to support for namespaces
(iii)there is no provision for inheritance from one DTDs to another
A. (i) is correct
B. (i),(ii) are correct
C. (ii),(iii) are correct
D. (i),(ii),(iii) are correct
5. A schema describes
(i) grammer
(ii) vocabulary
(iii) structure
(iv) datatype of XML document
A. (i) & (ii) are correct
B. (i),(iii) ,(iv) are correct
C. (i),(ii),(iv) are correct
D. (i),(ii),(iii),(iv) are correct

Answers
1. What does XML stand for?
A. eXtra Modern Link B. eXtensible Markup Language
C. Example Markup Language D. X-Markup Language
2. Which statement is true?
A. All the statements are true B. All XML elements must have a closing tag
C. All XML elements must be lower case D. All XML documents must have a DTD
3. What does DTD stand for?
A. Direct Type Definition B. Document Type Definition
C. Do The Dance D. Dynamic Type Definition
4. Disadvantages of DTD are
(i)DTDs are not extensible
(ii)DTDs are not in to support for namespaces
(iii)there is no provision for inheritance from one DTDs to another
A. (i) is correct
B. (i),(ii) are correct
C. (ii),(iii) are correct
D. (i),(ii),(iii) are correct
5. A schema describes
(i) grammer
(ii) vocabulary
(iii) structure
(iv) datatype of XML document
A. (i) & (ii) are correct
B. (i),(iii) ,(iv) are correct
C. (i),(ii),(iv) are correct
D. (i),(ii),(iii),(iv) are correct

Introduction to XML

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