Architecture of a typical Web application

Examples: Electronic games, help subsystems, kiosks

Architecture of a stand-alone Web application

Released as Tcl packages

Tcl is easily embedded in other languages, legacy applications

Tcl is widely available: Unix, Windows 3.1/95/NT, Macintosh

Tcl is free: no licensing required

Document Handling Package

WWW Megawidget

Basic function: Retrieves WWW documents from a server

Why?

What should a DHP do?

Single command: document

document loaduri URL

package require Document
namespace import Document::document

document configure -cachedirectory MyCache
document loaduri relative.html http://myHost/some/path/

Scheme handlers, media types, encodings, etc, may be added at runtime

Various features:

• Document meta-data separate from load meta-data
• Document disposition - targets
• Concurrent loads
• Prioritised queueing system

API for scheme handlers and media type processors

A system for enrolling students in tutorials & laboratories

Supervisor interface uses standard Web browser

Readily available, convenient to use

Student interface uses customised user agent

As simple & intuitive as possible, avoids unauthenticated/unauthorised Web browsing

Demo

Megawidgets behave just like real Tk widgets

WWW megawidget architecture:

Supports HTML v3.2, CSS1 stylesheets, Tclets

Separate HTML parser, also XML parser

Uses Tk Text widget for display

Can be used like any other Tk widget

Modelled on Tk scrollbar/scrollable widget connections

WWW widget is configured to use document command

document load targets widget's method

www .www	;# Creates a WWW megawidget called .www

.www configure -loadcommand {document loaduri -target {.www load}}

Final releases of v1.0 of DHP and WWW megawidget

Include CDF support for "smart pull"

Server support

The Document Handling Package provides easy-to-use, high-level management of Web document retrieval

The WWW and HTML megawidgets allow an application to display HTML documents, and XML documents in the future