Introduction to XML

CS348 Information System

Guest Lecture

Hazem Elmeleegy

Outline

What is XML? Syntax of XML Document

DTD (Document Type Definition)

XML Query Language XML Databases

XML Schema

Oracle JDBC

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

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

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. c

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,LASTNAME)>

<!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. )

Oracle JDBC (Example)

Import java.sql.*;Import java.io;Class simple{ public static void main(String[] args) throws Exception{ Connection conn=null; try{

String conStr = "jdbc:oracle:thin:@oracle.cs.purdue.edu:1521:orb";

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());

conn = DriverManager.getConnection(conStr,”username”,”passwd");

Statement cursor = conn.createStatement(); // Connection Est.

ResultSet rset = stmt.executeQuery(“Select* from table_name”);

while(orset.next()){

System.out.println(“Printing column name ”+orest.getStringVal(1));

}

}Catch(ClassNotFoundException e){} cursor.close(); conn.close(); }}

References [1] Database Management Systems by Ramakrishnan and Gehrke

Thank You