World Wide Web Background

What Is Dynamic HTML

• Dynamic HTML is normal HTML, but is generated on the fly by the serving computer for each incoming request.
• Any program the server invokes can generate this HTML.
• Typically servers are carefully configured as to how to locate and execute specified HTML generating programs.
• The HTML generating program is invoked as a result of a special URL (address) recognized by the web server (in our case Apache).
• The HTML generating program is typically launched as a unique process that serves one and only one request by one and only one user.
• If many users simultaneously ask for the same dynamic HTML page, many copies of the HTML generator program are simultaneously launched. Each user gets their own unique instance of the HTML generator program.
• The dynamic HTML generating program has several available sources of input information.
  • Addressing infomation (the requested URL).
  • Any and all accessible server resources (for example Unix).
  • Discrete bits of information (cookies).
  • Any persistent data previously stored (i.e. local database).
  • Any "form" data supplied from the client browser.
• What are the advantages of dynamic HTML?
  • Fully customizable on the fly for each server "customer".
  • Can maintain state information.
  • Can perform conditional logic.
  • Can be customized based on user preferences.
  • Can leverage other resources (i.e. database).
• What are the limitations of dynamic HTML?
  • Often more complex to create.
  • Can be a security liability.
  • Demands much higher server resources.
  • Can be slow.
  • Can fail in interesting and obscure ways.