- From: Loretta Guarino Reid <lguarino@adobe.com>
- Date: Tue, 19 Apr 2005 15:45:52 -0700
- To: w3c-wai-gl@w3.org
Historically, we referenced UAAG 1.0 to avoid reinventing the wheel for Web apps. Therefore, I don't think that Web content is actually ever used to create a user agent, instead it creates a Web app. The proposed (and somewhat contentious) differences between Web app and user agent: A Web app is the delivery unit and the user agent creates the perceivable unit. Scripting is part of the delivery unit but may effect the perceivable unit. The perceivable unit is differentiated from the user agent in that the perceivable unit is contained in a viewport (or multiple viewports). The perceivable unit does not contain user agent user interface controls such as prompts, menus, and alerts. Although, scripting can be used to generate additional viewports (such as pop-up windows, dialogs, etc.) [@@may cause more confusion than clarity?] User agent, as defined in UAAG 1.0 [1] is,"In this document, the term "user agent" is used in two ways: 1. The software and documentation components that together, conform <<http://www.w3.org/TR/UAAG10/conformance.html#Conformance>http://www.w3.org/TR/UAAG10/conformance.html#Conformance> to the requirements of this document. This is the most common use of the term in this document and is the usage in the checkpoints. 2. Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins <<http://www.w3.org/TR/UAAG10/glossary.html#def-plug-in>http://www.w3.org/TR/UAAG10/glossary.html#def-plug-in>, and other programs including assistive technologies <<http://www.w3.org/TR/UAAG10/glossary.html#def-assistive-technology>http://www.w3.org/TR/UAAG10/glossary.html#def-assistive-technology> that help in retrieving and rendering Web content." [1] <<http://www.w3.org/TR/UAAG10/glossary.html#def-user-agent>http://www.w3.org/TR/UAAG10/glossary.html#def-user-agent> [2] Definitions of delivery unit and perceivable unit available at: <<http://www.w3.org/TR/di-gloss/>http://www.w3.org/TR/di-gloss/> Examples to show differences between a web app and a user agent 1. an applet The java code is the delivery unit. It includes information about how to react to user input (i.e., the methods, event handlers) the interface is rendered by and the interaction is handled by the java virtual machine - the user agent. i.e., the virtual machine instantiates event handlers (as defined by applet code) then catches the user input and sends it to the event handlers. in other words, the applet tells the virtual machine what event handlers to set up and how they should work, but the VM is doing the work. 2. a flash web site The swf file is the delivery unit. The interface is rendered by and the interaction is handled by the flash player - the user agent. Even in the example where the flash author needs to describe what information should be passed to an assistive technology (via the user agent/flash player), it is the player that follows the instructions in the swf about what and how and when to do those things. 3. javascript+html+css javscript+html+css is the delivery unit. It includes information about how to react to some user input (i.e., event handlers for onClick, etc.). The interface is rendered by and the interaction is handled by the javscript interpreter. the script tells the interpreter (embedded in the user agent) what event handlers to set up and how they work, but the UA is doing the work. 4. AJAX <<http://www.adaptivepath.com/publications/essays/archives/000385.php>http://www.adaptivepath.com/publications/essays/archives/000385.php> real-life example: Google Suggests <<http://www.google.com/webhp?complete=1>http://www.google.com/webhp?complete=1> 5. Web service <<http://java.sun.com/webservices/docs/1.2/tutorial/doc/>http://java.sun.com/webservices/docs/1.2/tutorial/doc/> - similar to AJAX but more.
Received on Tuesday, 19 April 2005 22:45:58 UTC