Introduction to XML

1. Introduction to XML CS348 Information System Guest Lecture Hazem Elmeleegy

2. Outline • What is XML? • Syntax of XML Document • DTD (Document Type Definition) • XML Schema • XML Query Language • XML Databases • Oracle JDBC

3. 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

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

5. 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.

6. DTD Example <!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”>]> <BOOKLIST> <BOOK GENRE = “Science” FORMAT = “Hardcover”> <AUTHOR> <FIRSTNAME> RICHRD </FIRSTNAME> <LASTNAME> KARTER </LASTNAME> </AUTHOR> </BOOK> </BOOKS> Xml Document And Corresponding DTD

7. 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

8. XML Schema • RDBMS Schema (s_id integer, s_name string, s_status string) • XMLSchema <Students> <Student id=“p1”> <Name>Allan</Name> <Age>62</Age> <Email>allan@abc.com </Email> </Student> </Students> <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

9. 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

10. 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)

11. 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”

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

13. 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

14. 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>

15. 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;

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

17. 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

18. 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 • StatementSQL statements without parameters • PreparedStatementSQL statements to be executed multiple times with different parameters • CallableStatementUsed for stored procedures

19. 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. )

20. 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(); } }

21. References • [1] Database Management Systems by Ramakrishnan and Gehrke

22. Thank You