Introduction. Web Pages. Example Graph

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1 COSC 454 DB And the Web Introduction Overview Dynamic web pages XML and databases Reference: (Elmasri & Navathe, 5th ed) Ch Web Database Programming Using PHP Ch XML: Extensible Markup Language Quotes The Web is -- by orders of magnitude -- the largest database ever created. Abiteboul, Buneman and Suciu, Data on the Web. Morgan Kaufmann, 2000 What makes the Web scenario different from classical databases? In short, everything. A database is a polished artifact. The Web is closer to a natural ecosystem. V. Vianu, A Web Odessey: from Codd to XML, SIGMOD Record, 32(2), June 2003 Lecture 9 - DB and the Web 1 Lecture 9 - DB and the Web 2 Lecture 9 - DB and the Web 3 Database - coherent design - rigid structure - queries - updates - transactions - concurrency - integrity - recovery All in a controlled environment Differences The Web - freely evolving - semi-structured - ever changing collection of data sources - interacting according to flexible protocols All in an uncontrolled environment Web Pages Static web pages Fixed content written in XHTML Example - course web pages Dynamic web pages Content depends on what you want and when you ask Requires scripting Online ordering Structured Semistructured Unstructured data Data Lecture 9 - DB and the Web 4 Lecture 9 - DB and the Web 5 Lecture 9 - DB and the Web 6 Seimstructured Data Example Bibliographic reference Some complete Some partial New types Example Graph Difference to Object Model Schema information (in SS data) is intermixed with the objects and their data values in the same data structure. No requirement for a predefined schema Lecture 9 - DB and the Web 7 Lecture 9 - DB and the Web 8 Lecture 9 - DB and the Web 9

2 Unstructured Data Very limited indication to type of data Example - a text document containing information embedded within it Web pages Static Page Example <html> <head>... </head> <body> <h2>project X</h2> <table width= 100% border= 0 > <tr> <td>john Smith</td> <td>32.5</td> </tr> <tr> <td>joyce English</td> <td>40</td> </tr> </table> </body> </html> Server-side Scripting Server executes script to create a web page to send to client Some data comes from the execution of the script PHP Personal home page PHP: Hypertext Preprocessor Lecture 9 - DB and the Web 10 Lecture 9 - DB and the Web 11 Lecture 9 - DB and the Web 12 Server-side Architecture PHP Open source general-purpose scripting language Many platforms Interpreted Libraries for DB access Example <html> <head>... </head> <body> <?php?> </body> </html> Your PHP script code goes here Lecture 9 - DB and the Web 13 Lecture 9 - DB and the Web 14 Lecture 9 - DB and the Web 15 Your First PHP Example <?php $file = $_SERVER['PHP_SELF']; $webpr = $_SERVER['HTTP_USER_AGENT']; $ipaddr = $_SERVER['REMOTE_ADDR']; echo "<p>you are running the file <b>$file</b>.</p>\n"; echo "<p>you are viewing this page using: <br /> <b>$webpr</b> <br /> from the IP address: <br /> <b>$ipaddr</b> </p>\n";?> First Result You are running the file /Sites/first_ex.php. You are viewing this page using: Mozilla/5.0 (Macintosh; U; PPC Mac OS x; en) from the IP address: Using a DBMS For Information Many pages access a DBMS for the data they display Use PHP to display the data Use DBMS to do the heavy work Lecture 9 - DB and the Web 16 Lecture 9 - DB and the Web 17 Lecture 9 - DB and the Web 18

3 How To Do It PEAR PHP Extension and Application Repository PHP database access function library Steps Connect to the DB Perform your query Display the results Always check for errors DBMS Example 1-1 require 'DB.php'; $d = DB::connect('oci8://user:pswd@ if (DB:isError($d)) { die("cannot connect ". $d->getmessage()); $d->seterrorhandling(pear_error_die); DBMS Example 1-2 $q = $d->query('select fname, lname, dno FROM EMPLOYEE'); while ($r = $q->fetchrow()) { echo "Employee $r[0] $r[1] works for department $r[2] \n"; Lecture 9 - DB and the Web 19 Lecture 9 - DB and the Web 20 Lecture 9 - DB and the Web 21 DBMS Example 1-3 $q = $d->query( 'SELECT fname, lname FROM EMPLOYEE WHERE dno =? AND salary >?', $_POST['emp_dno'], $_POST['salary']); echo "Employees in dept $_POST['emp_dno'] " echo "with salaries more than $_POST['salary'] are: \n"; while ($r = $q->fetchrow()) { echo "$r[0] $r[1] \n"; DBMS Example 1-4 $all = $d->getall('select fname, lname, dno FROM EMPLOYEE'); foreach ($all as $a) { echo "Employee $a[0] $a[1] works for department $a[2] \n"; Inexact Syntax What s missing from the previous examples? The appropriate XHTML tags. Lecture 9 - DB and the Web 22 Lecture 9 - DB and the Web 23 Lecture 9 - DB and the Web 24 DBMS Example 2 $all = $d->getall('select fname, lname, dno FROM EMPLOYEE'); echo "<table>"; echo "<tr><td>first</td><td>last</td><td>dno</td></tr>"; foreach ($all as $a) { echo "<tr><td>$a[0]</td><td>$a[1]</td><td>$a[2]</td></tr> \n"; echo "</table>"; Other Possibilities Most anything you can do with SQL, you can do with PHP and SQL. Examples Create tables Insert rows Alter data Delete rows Let DBMS Do Heavy Work Joins Sorts Statistical calculations In contrast to some systems Yes, Ruby on Rails, I m looking at you! Lecture 9 - DB and the Web 25 Lecture 9 - DB and the Web 26 Lecture 9 - DB and the Web 27

4 XML - In the Beginning SGML - Standard Generalized Markup Language 1960s Charles Goldfarb, Edward Mosher and Raymond Lorie (GML) Designed for sharing machine-readable documents in large projects Must last for many years WYSIWYG Original Embedded commands WYSIWYG Enter WWW Created by Tim Berners-Lee in 1991 Originally text based HTML based on SGML Very simple Lecture 9 - DB and the Web 28 Lecture 9 - DB and the Web 29 Lecture 9 - DB and the Web 30 Along Came Pretty Formatting Formatting tags Browser extensions Standards lagged implementations Some deliberate deviants Data Storage and Exchange Organisations and Applications need to exchange data Binary files Structured text files Enter XML Extensible Markup Language Describes methodology for structuring documents XML Working Group of W3C Can be used for other data sets Lecture 9 - DB and the Web 31 Lecture 9 - DB and the Web 32 Lecture 9 - DB and the Web 33 XML Documents XML Markup XML Tags Streams of characters Document s content Markup Structure of content Nature of content Bibliography example Idea is to label content according to structure Commonly called tags Begin with <tagname> End with </tagname> Structure content goes between the tags XML does not define the set of tags Tags can have attributes <Elementname attname1= attvalue1 attname2= attvalue2... > <subsection author= Simon moddate= 31/1/ > Lecture 9 - DB and the Web 34 Lecture 9 - DB and the Web 35 Lecture 9 - DB and the Web 36

5 Well-Formed vs. Valid Well-Formed Nested No overlapping tags Valid Conforms to a DTD or XML Schema Enter DTD Document Type Definition Defines the element names, their attributes, order, number Example XML document Example DTD DTD 1 * Repeated zero or more times (optional multivalued element) + Repeated one or more times (required multivalued element)? Repeated zero or one times (optional single-valued element) An Element without any symbol must appear exactly once. Lecture 9 - DB and the Web 37 Lecture 9 - DB and the Web 38 Lecture 9 - DB and the Web 39 DTD 2 DTD 3 XML and Data The type of the element is in parenthesis following the element. If the parenthesis include element names, these are children of the element. If the parenthesis includes #PCDATA or other data types, the element is a leaf node. Parenthesis can be nested when specifying elements. (e 1 e 2 ) - the bar means that either e 1 or e 2 can appear in the document. Hierarchical structure Useful for data exhange Standard public DTDs Lecture 9 - DB and the Web 40 Lecture 9 - DB and the Web 41 Lecture 9 - DB and the Web 42 XML Schema XML Schema example: see Ch 27 of Elmasri and Navathe More comprehensive specification Storing XML Documents Files Use DBMS to store documents as text Use DBMS to store document contents as data elements Specialised system for storing native XML data Extract XML from DBMS Lots of data exists in DBMSs Can be extracted for Web display or data exchange Lecture 9 - DB and the Web 43 Lecture 9 - DB and the Web 44 Lecture 9 - DB and the Web 45

6 Some Issues XML uses a hierarchical model RDBMS use flat relational model When referential integrity is added, relational schema can be considered a graph structure Example ER Diagram Subset ER Diagram Lecture 9 - DB and the Web 46 Lecture 9 - DB and the Web 47 Lecture 9 - DB and the Web 48 COURSE as Root STUDENT as Root SECTION as Root Lecture 9 - DB and the Web 49 Lecture 9 - DB and the Web 50 Lecture 9 - DB and the Web 51 Breaking Cycles Lecture 9 - DB and the Web 52

Chapter 13 XML: Extensible Markup Language

Chapter 13 XML: Extensible Markup Language - Internet applications provide Web interfaces to databases (data sources) - Three-tier architecture Client V Application Programs Webserver V Database Server