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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 • • • • 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 – – – – 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 – – – – 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