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Database-WWW Integration
Brenda Lowndes
Computing Services Department
The University of Liverpool
Running an Institutional Web Service
16-17th July 1997
Database-WWW Integration
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What is Database-WWW Integration?
Why integrate a database with the Web?
How is data integrated?
What tools are available?
Running an Institutional Web Service
16-17th July 1997
What is Database Integration?
• Using the information in a database to
create Web pages
• Using a Web browser to access data in a
database
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
Why Use the Web to Access Data?
• Familiar interface
• Data can be integrated with other
information in an institution’s 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
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
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.
Running an Institutional Web Service
16-17th July 1997
When should you use Static Access?
• Non volatile data
• Fixed or small number of pages
• Predefined requests to the database
– No ad-hoc queries
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
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
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DBPerl
Embedded SQL
DBMS report writers
DBMS scripting language
Running an Institutional Web Service
16-17th July 1997
Running a Program
Web Server
CGI
HTML
Running an Institutional Web Service
16-17th July 1997
Running a Program
Web Server
CGI
Database Networking Software
HTML
Database Client
Web Client
Database Networking Software
Running an Institutional Web Service
16-17th July 1997
Running a Program
Web Server
CGI
ODBC Driver
HTML
Database Networking Software
Database Networking Software
Running an Institutional Web Service
16-17th July 1997
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
HTML Templates
HTML
Template
Web Server Server Extension
HTML
Running an Institutional Web Service
Database
Networking Software
16-17th July 1997
Internet Database Connectivity
• Microsoft’s 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
Running an Institutional Web Service
16-17th July 1997
•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
Server-side Scripts
Active
Page
VBScript
Java
Web Server Filter
HTML
PL/SQL
LiveHTML
Client/Server
Running an Institutional Web Service
16-17th July 1997
Stateless Connection
• Previous access methods do not maintain a
session between the server and the database
• The client requests the data
• The server
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connects to the database
produces the HTML
delivers the page to the client
disconnects from the database
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
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
Running an Institutional Web Service
16-17th July 1997
Java and JDBC
Web Server
Java Applet
Java
Applet
Running an Institutional Web Service
16-17th July 1997
Java and JDBC
Java
Applet
Java
Applet
Running an Institutional Web Service
Web Server
Java Applet
Java
JDBC
16-17th July 1997
What Tools are Available?
See:
http://www.liv.ac.uk/~qq48/publications/html/dbweb.html
Running an Institutional Web Service
16-17th July 1997