DatabaseWWW Integration

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Database-WWW Integration

• Brenda Lowndes
• Computing Services Department
• The University of Liverpool

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Database-WWW Integration

• What is Database-WWW Integration?
• Why integrate a database with the Web?
• How is data integrated?
• What tools are available?

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What is Database Integration?

• Using the information in a database to create Web
  pages
• Using a Web browser to access data in a database

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Why Use a Database to Produce Web Pages?

• Institutional data is usually stored in a
  database.
• Data is being replicated in HTML pages
• Duplication of data and effort
• Inconsistencies in the data
• Difficult to merge updates
• Web pages can be updated automatically whenever
  the database is updated

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Why Use the Web to Access Data?

• Familiar interface
• Data can be integrated with other information in
  an institutions web pages
• Platform and vendor independent front-end
• Client machine does not need database
  networking software
• Information can be made available to anyone on
  the Internet

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Using a Web Browser to Access a Database

• Web pages and forms are used to provide access to
  the database
• Database can be queried or updated

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How is Data Accessed?

• Relational Databases
• HTML pages are generated from the database
• statically
• dynamically
• Java and JDBC downloaded and run on the client
  machine or on the server
• Library catalogues, Z39.50 servers, other free
  text search and retrieve

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Static Access

• A program runs offline to produce the HTML pages
• Pages copied into web server directories
• Can be automated and scheduled to run
• at specific times
• triggered by a database update

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Producing Static HTML Pages

• Any program that can access the database and
  output HTML
• programming language and embedded SQL
• report writers
• database scripting language
• Database and Web development software provides a
  Save as HTML option.

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When should you use Static Access?

• Non volatile data
• Fixed or small number of pages
• Predefined requests to the database
• No ad-hoc queries

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Dynamic Access

• HTML pages are generated from the database when
  the page is requested
• Data always up to date
• HTML forms can be used to define specific data
  that is to be retrieved
• Many different pages can be generated

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Pages are created by

• Running a simple program on the server which
  outputs HTML
• Extensions to the server which embed data
  extracted from the database into an HTML template
  file
• Server-side scripts which access the database and
  output HTML

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Using a Program on the Server

• Typically a series of print statements that
  output the whole HTML page
• Usually run as a cgi program
• Written using
• DBPerl
• Embedded SQL
• DBMS report writers
• DBMS scripting language

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Running a Program
HTML
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Running a Program
HTML
Client/server Access
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Running a Program
Database Networking Software
HTML
Database Client
Database Networking Software
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Running a Program
CGI
ODBC Driver
HTML
Database Networking Software
Database Networking Software
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Template Files

• Template specifies
• where the database is
• what data is required
• what HTML is output
• Process can be server filter or extension, plug
  in or cgi script

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HTML Templates
HTML Template
Server Extension
HTML
Database Networking Software
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Internet Database Connectivity

• Microsofts IDC is an extension of their Internet
  Information Server
• Uses two files
• .IDC file provides information about the database
  and the SQL queries used
• .HTX file provides the HTML template into which
  the data from the database is embeddded

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Advantages of Using Templates

• Pages easier to write than full programs
• Requires only a knowledge of HTML and how to
  specify an SQL query
• Web development tools from Microsoft and other
  suppliers often automate the process

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Internet Database Connectivity

• Microsofts database products have wizards to
  produce IDC/HTX files automatically
• Microsofts Web development software -Frontpage,
  Visual Interdev etc will generate IDC/HTX files
• Web development tools from other suppliers will
  also generate IDC/HTX files

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Server-side Scripts
Active Page
Filter
HTML
Client/Server
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Active Server Pages

• Microsoft Internet Information Server 3.0
• Server-side execution environment
• Can access any ODBC database
• Output is HTML- suitable for any browser
• Maintain a connection to the database

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Stateless Connection

• Previous access methods do not maintain a session
  between the server and the database
• The client requests the data
• The server
• connects to the database
• produces the HTML
• delivers the page to the client
• disconnects from the database

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Maintaining a Connection

• Many servers now can maintain a session between
  subsequent requests from the client
• These servers can maintain a connection to the
  database
• Can define a record set and scroll through
  records
• Database connection can be closed by a request
  or timed out after a defined period of inactivity
  or when the server is shut down

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Java and JDBC

• JDBC is a Java API for executing SQL statements
• JDBC statements in a Java applet are used to
  access virtually any relational database
• The Java applet is downloaded to the client
• The client establishes the connection with the
  database server

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Java and JDBC
Java Applet
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Java and JDBC
Web Server
Java Applet
Java Applet
Java JDBC
Java Applet
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What Tools are Available?

• See http//www.liv.ac.uk/qq48/publications/html/
  dbweb.html