IWMW 1997: Database-WWW Integration
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This document discusses database-WWW integration, including: - Using a database to dynamically generate web pages or access data through a web browser. - Benefits include reusing existing institutional data, automatic updates, and platform independence. - Data can be accessed statically by pre-generating HTML pages or dynamically by programs that connect to the database and output HTML on request. Popular integration tools include server-side scripts, templates, and Java Database Connectivity (JDBC).
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IWMW 1997: Database-WWW Integration
- 1. 16-17th July 1997Running an Institutional Web Service Database-WWW Integration Brenda Lowndes Computing Services Department The University of Liverpool
- 2. Database-WWW Integration • What is Database-WWW Integration? • Why integrate a database with the Web? • How is data integrated? • What tools are available?
- 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
- 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
- 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
- 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
- 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
- 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.
- 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
- 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
- 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
- 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
- 13. Running a Program HTML CGIWeb Server
- 14. Running a Program HTML CGIWeb Server Database Networking Software Database Networking Software Database Client Web Client
- 15. Running a Program HTML CGIWeb Server ODBC Driver Database Networking Software Database Networking Software
- 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. HTML Templates HTML Server ExtensionWeb Server Database Networking Software HTML Template
- 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
- 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. Server-side Scripts HTML FilterWeb Server Client/Serve r VBScript Java PL/SQL LiveHTML Active Page
- 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
- 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
- 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
- 24. Java and JDBC Java Applet Web Server Java Applet
- 25. Java and JDBC Java Applet Web Server Java Applet Java JDBC Java Applet
- 26. What Tools are Available? See: http://www.liv.ac.uk/~qq48/publications/html/dbweb.html
Editor's Notes
- Currently, database integration with the Web appears to be one of two things Constructing Web pages from data stored in a database Using Web browsers and software on the Web server to retrieve and update data in a database
- To avoid duplication of effort and prevent inconsistencies, data should be stored in only one place. It is easier to produce HTML pages from data stored in a database than to produce a database from data in HTML! If the Web page is refreshed whenever the data in the database changes or if the database is accessed dynamically, the most up to date data is always available from the Web page.
- The Web browser has become one of the most widely used pieces of software. Using a Web browser, staff in an institution are able to access data using a familiar interface. The data appears in the Web pages without the user knowing where the data has come from. By accessing the data using a Web browser, the data is delivered to the user as just another HTML page. Access to the data can be controlled. Data can be made available only via an intranet or it can be made available to anyone on the Internet..
- Web browsers are being used as the client software. This provides a front-end to the database that is independent of the database vendors client software. This provides a platform-independent front-end. The Web server acts as the database client. The Web client does not access the database directly and does not need to have the database networking software installed.
- Only discussing access to data in relational databases here.
- Database systems and Web development software provide the tools and wizards to automate and schedule the page updates.
- Microsoft Access will generate HTML pages based on tables, forms, reports and queries. It also provides simple ‘switchboard’ pages to connect the pages together. Most of the well-known Web development packages will generate static pages from an associated database.
- When using static pages, all the requests to the database must be anticipated. It is not possible to build up a query and select only those records in the database that match the query.
- Queries can be built up from information entered on an HTML form. The data retrieved from the database is then embedded into the HTML returned.
- Perl often used to write cgi-scripts. DBPerl is an library of functions that can be called from Perl to access data in a database. It incorporates ingperl, oraperl etc. Some DBMS scripting languages provide higher level functions to generate HTML code.
- Configuration when the database is available on the Web server. The database does not need to be on the Web server but must be in a directory (or share) accessible from the server.
- Configuration when database is on a separate database server. Database client networking software must be installed on the Web server. The Web client does not require database client software or networking.
- The Web server may be configured to access a specific database server. (e.g. an Oracle server)
- Amore general solution uses ODBC to connect the Web server to the database server. The Web server is able to access any database, if it has the appropriate ODBC driver installed. Some, but not all ODBC drivers also require the database networking software to be installed