Intro. to Content-Driven

(dynamic) Web Sites

Gerry Santoro

Assistant Professor

School of Information Sciences and Technology

This document is located at URL:

http://students.ist.psu.edu/~santoro/seminars/cdis.htm

Overview of Seminar

Purpose: To describe the various methods for developing content-driven information systems on the Web.
Outline of seminar:
- Describe how content-driven Web sites work.
- Explain how databases can be used to solve information problems.
- Explain the role of database structure in developing dynamic sites.
- Distinquish between static and dynamic information.
- Explain differences between client-side and server-side scripting.
- Introduce Structured Query Language.
- Describe various approaches to content-driven sites.
- A simple example using Open Source method.
- Many resources along the way.

Content-Driven (Dynamic) Web Sites

Dynamic Web sites involve the use of scripts and (often) database back-ends.

A few definitions:
- database - a collection of data organized in some way that makes it useful
  Most DBMSs is use today follow a relational model. (ie, MS Access)
- form - an object used to present or receive data, the primary user interface
- scripts - program segments that provide functionality
any database-driven application uses programs/scripts/forms to form an interface between the data and the user
The user never directly manipulates the database.
- security checks
- audit trails
- exception handling
- data validity
For a Web-based application, the Web form is the user interface.
Typicaly some programming language (such as Visual Basic) and some version of SQL are used for the database interaction scripting.
The way it works:
- Web page form (perhaps with some javascript support) gets input from user.
- User input is sent as byte stream to set of programs (running on server) that query (or perform some operation on) the database.
- Result of query is returned as an HTML stream to the client.
  Ex: the CalSky database which can be customized to a users location and time.
- Most online databases follow the relational model. (Although the object-oriented databases are growing in popularity.)
  Regardless of the DBMS or database model you use, give lots of thought to the STRUCTURE of your database.
- The database structure means determining, for each field:
  - field name, data format and size
  - arrangement into tables
  For categorical fields it is also important to define the available categories.
  The reason this is very important is that it could be VERY EXPENSIVE to alter the database structure (and support scripts) after data has been entered.
- Remember that a database can only be used to solve problems in four ways.
  - virtual filing cabinet
  - subset of data based on query
  - aggregated picture of data based on report
  - data-mining (still very new)
  Your analysis and development of the structure will benefit by your defining the problem - and then determinimg the types of queries and reports needed to solve the problem.
  Also remember to INVOLVE THE USER if possible!

Static versus dynamic Information

By its nature, some information is dynamic, and lends itself to a database backend.
Ex: search engine, TV guides, weather pages, sports pages, news pages, etc.
Accessability and usability are even more important with dynamic sites -- since the user now has to understand HOW to affect the site dynamics.
If you build it -- will anyone come?
Ways that information can vary dynamically:
- by time
- by location
- by user characteristic
- by user interest
- in response to changing environment
User choices, and the nature of user command, must be accessible to the user
If any system (even one Web based) is hard to use, most users will give up if at all given the chance.
Modeling user interactions is important when designing interactive sites
Scenarios (as per Jack Carroll) are one approach to designing human/system interactions.

Programming for Dynamic Web Sites

Your choices will be somewhat limited by the servers available to you. (This could be an ISP issue.)
For example, PSU ITS only supports Perl scripting from an Apache server in the psu.edu domain -- and even then with certain restrictions.
Another issue is where the processing happens:
- server-side - more consistency but may bog-down server
- client-side - inconsistent
- mixed client/server processing - new approach, aids in fine-tuning for above issues
How the programs talk to the DBMS
- SQL (structured query language) provides a way for your programs to talk to a DBMS engine.
  Here is a link to an SQL tutorial from BayCon Group.
CGI
- CGI (common gateway interface) is a server-side scripting protocol
  - STDIN and STDOUT used for comm channel between Web server and program
  - all data sent as a single byte stream
- languages used will vary according to the server
- Many CGI libraries are available for you to use/learn.
- The scripts.cac.psu.edu server will support script testing for perl scripts
  An example: perl script.
- I recommend use of CGI and Perl for learning how to prorgam for dynamic sites. Make use of Perl script libraries that can be altered with minimum effort for your need.
Active Server Pages (ASP)
- love them or hate them -- Microsoft is a MAJOR player and ASP is its chosen method (for now).
- Makes use of MS servers, Visual Basic or VB script, and some version of SQL (such as MS SQL Server 2000).
- Works well with MS-Access (jet engine) DBMS back-end.
- Alas - PSU ITS does not support ASP.
  If you want to learn ASP - my suggestion is to set up your own server. MS-IIS or PWS will work. This is a GREAT way to learn about Web databases -- but be VERY careful about security!
- One of many great ASP learning resources learnASP.com
Cold Fusion (Macromedia) is a scripting language and set of server extensions that provide for interactive DBMS-driven web sites.
A DBMS and Web server are still needed.
Some advantages of Cold Fusion are:
- support (from Macromedia)
- Intergrates well with Dreamweaver, Fireworks, and Flash

The Open Source Approach

Why I favor this approach:

servers are free
lots of support from peers through open source community

Where can you get servers?

hotscripts.com
Fully-configured complete server (plus utility) sets for your operating system.

Reference sites?

php.net
apache.net
mysql.com

Structured Query Language

The greatest power of the DBMS lies in its ability to run fast and powerful queries
SQL was originally developed to allow program front-ends to be developed for database-driven business systems.
In the case of the dynamic Web site, the Web server and client provide the system front-end (user interface).
SQL can be accessed through various means - although I recommend always practicing with a command-line interface.
demonstrate some commands
For more on SQL see the MySQL docs or w3schools.com
It is possible to start SQL slowly - do not be overwhelmed as entire careers can be made out of SQL.

PHP and the Methodology

PHP is a powerful and easy server-side scripting language
- Currently there is no PSU support for PHP
- PHP has the advantage of being a language designed for Web scripting -- so it has certain structures that make common tasks more efficient, straightforward, etc.
- A great resource is PHPHelp.com.
- There are many great open-source server suites
- PHP example
requires Apache to be compiled and loaded with PHP extensions -- that enables the Web server to recognize and process PHP code.
pages can be html with inline php or php with inline html
Either way - the output is an html stream.
html forms provide user-input and control
php scripts use special functions to open SQL databases and issue queries
Results of queries are returned as arrays.
PHP was designed for the Web and interfaces grandly with the server.
So coding is straightforward and easy.
Plus there are MANY script libraries.

An example -- The Happy Valley Rider Board

Happy Valley Rider Board

Database Structure

Site Flowchart

This page is maintained and made available for educational use by Dr. Gerry Santoro, gms@psu.edu