1. Accessing Relational Databases from the World Wide Web by Tam Nguyen & V. Srinivasan Presented by Megan Thomas and Randi Thomas CS294-7 February 11, 1999

2. Outline Overview from the User’s perspective Step through the path of a single query Brief Clarification of the Macro Language Alternative Approach to DB2 WWW Advantages of DB2 WWW System Disadvantages of DB2 WWW System What’s Not Presented in the Paper

3. Overview of the Whole Shebang User asks for form User fills out HTML form Query report in HTML DB2 WWW Macro file URL HTML form SQL Query results HTML form data HTML You Are Here

4. First Step How user got here is irrelevant! First URL used: http://[{web-server}]/cgi-bin/db2www[.exe] /{macro-file}/{input}[?name=val&…] Web server starts db2www cgi-bin program db2www program: – uses macro-file to create HTML form – sends HTML form back to the user User fills out HTML form containing the information which will drive the SQL query

5. HTML Input Form

6. Second Step Second URL used: http://[{web-server}]/cgi-bin/db2www[.exe] /{macro-file}/{report}[?name=val&…] web server starts db2www cgi-bin program db2www program uses macro-file to: –translate data in HTML input form into SQL –submit SQL query to DB2 database –translate database results into HTML db2www sends HTML report to user

7. HTML Report Form

8. Macro Language (Bulk of Paper) Definition: A mechanism for cross language variable substitution between: –HTML input and SQL query strings –SQL query results and HTML output A Macro Contains: –SQL “sections” –HTML “sections” –Variable substitutions which tie the “sections” together Example in Back up slides

9. What’s In A Macro File? One or more Variable Definition Sections: –Used to define and manipulate macro variables One or more SQL Command Sections: –Contains one SQL statement –May contain a user-defined report format for the SQL statement (optional) One HTML Input Section: –Used to get input variable values from user One HTML Report Section: –Used to generate reports from SQL query results

10. Alternative Approach to DB2 WWW Stand-alone cgi program (for each application) to: – accept and generate HTML – access the database This cgi program would need alteration in order to: –use new HTML features –use new SQL features –or to conform to changes in: cgi protocol or DBMS API

11. Advantages of DB2 WWW System Application programmer can focus on desired –HTML input/output forms –SQL queries Programmer is not encumbered with the translation mechanisms Is a General Purpose solution: –Encompasses all of HTML and SQL

12. Disadvantages of DB2 WWW System Process startup overhead: –Two db2www processes are started per query: One to send the appropriate HTML input form One to do the query and send the HTML report Application logic that cannot be expressed in HTML or SQL cannot be done

13. Not Presented in This Paper DB2 WWW Transactional support: –Can be done in two ways: Whole macro can be one transaction Each SQL statement is a separate transaction –Not clear how this is done DB2 WWW Security will work with: –Web Server –DBMS –Firewalls –Not clear how this is done Other DBMSs

14. Not A Real Slide --> FYI DB2 WWW Transactional support: –Not clear how this is done DB2 WWW Security will work with: –Not clear how this is done Joe - not clear how this stuff is done because the on-line reference to the DB2 WWW Connection Application Developers Guide is dead

15. Back up Slides

16. URL Explanations http://[{web-server}]/cgi-bin/db2www[.exe] /{macro-file}/{cmd }[?name=val&…] db2www[.exe]: –cgi-bin program macro-file: –file written in DB2 WWW macro language for cross-language variable substitution If cmd is: –“input”: db2www processes the HTML input section of the macro-file –“report”: db2www processes the HTML report section of the macro-file [?name=val&…]: –Optional input variables from the Web client

17. HTML to create HTML FORM

18. Sample Macro file: Variable Definition Section

19. Sample Macro file: SQL Command section

20. Sample Macro file: HTML Input Section

21. Sample Macro file: HTML Report Section

22. Web Browser Web Server DB2 WWW Gateway Query Tools HTML Editor Macro File: SQL Command input form report form User RunTime Environment Application Development Environment HTML forms SQL Query CGI HTML forms & SQL command