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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
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
Overview of the Whole Shebang
You Are Here
User asks for
form
URL
DB2 WWW
HTML form
Macro file
User fills out
HTML form
HTML form data
SQL
DB2 WWW Query results
Query report
in HTML
HTML
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
HTML Input Form
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
HTML Report Form
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
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
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
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
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
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
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
Back up Slides
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
HTML to create HTML FORM
Sample Macro file:
Variable Definition Section
Sample Macro file:
SQL Command section
Sample Macro file:
HTML Input Section
Sample Macro file:
HTML Report Section
Application Development
Environment
HTML
Editor
HTML
forms
User RunTime
Environment
Web
Browser
Query
Tools
SQL Query
Macro File:
•SQL Command
•input form
•report form
HTML forms
& SQL command
Web
Server
CGI
DB2 WWW
Gateway