Database-WWW Integration: Running an Institutional Web Service

1. Database-WWW Integration Brenda Lowndes Computing Services Department The University of Liverpool Running an Institutional Web Service

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. CGI Web Server Running a Program HTML Running an Institutional Web Service

14. CGI Web Server Web Client Running a Program Database Networking Software HTML Database Client Database Networking Software Running an Institutional Web Service

15. Web Server Running a Program CGI ODBC Driver HTML Database Networking Software Database Networking Software Running an Institutional Web Service

16. 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

17. Web Server HTML Templates HTML Template Server Extension HTML Database Networking Software Running an Institutional Web Service

18. 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

19. 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

20. VBScript Java Web Server PL/SQL LiveHTML Server-side Scripts Active Page Filter HTML Client/Server Running an Institutional Web Service

21. 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

22. 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

23. 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

24. Web Server Java Applet Java and JDBC Java Applet Running an Institutional Web Service

25. Java and JDBC Web Server Java Applet Java Applet Java JDBC Java Applet Running an Institutional Web Service

26. What Tools are Available? See: http://www.liv.ac.uk/~qq48/publications/html/dbweb.html Running an Institutional Web Service