Re[2]: Content Negotiation and Adaptation, Why and How .. ?

Hi Mark,

 

>I don't know that "complete" is a necessary goal for what you want to

>achieve

 

Sure, in a particular use case we will not need to obtain the complete characteristics and capabilities of a particular element (such as a device, a document, a server, etc.). However, in order to provide a complete content negotiation and adaptation solution, we must have a model, or a tool, that allows to give any wanted description that can help to achieve the adapted services delivery. You can have a look on such model, in : 



http://opera.inrialpes.fr/people/Tayeb.Lemlouma/NegotiationSchema/index.htm

 

Where a basic schema was defined on top of the CC/PP model, and this specially for a general negotiation and adaptation framework. These schemas are used in practice in an implemented prototype called NAC: http://opera.inrialpes.fr/people/Tayeb.Lemlouma/Papers/ANegoP.pdf

 

> And the more information that is available, the

> better that adaptation will be.

 

Of course the more but only the utile information, don't forgot that the problem is posed in the context of heterogeneous environments, where:

 

- Devices players haven't advanced power processing, so adaptation in the client side (such as tailoring CSS style sheet to the original document) must be reduced or avoided. 

 

- Low bandwidth, so the control message exchange, such in our case "the negotiation-oriented messages exchange" must be minimized (see our last position paper to the W3C delivery context Workshop 

http://opera.inrialpes.fr/people/Tayeb.Lemlouma/Papers/W3C/UniversalProfilingForContentNegotiation/W3CPositionPaper03-2002.htm ).

 

>For example, you might have the following local rules which you declare

>independantly;

>

>- WML content gets translated to XHTML Basic

>- English content gets translated to French

>

>The resultant mesh would take any English WML and produce French XHTML

>Basic.

 

Rules like that are applied during the step called "the matching" of the environment parameters. 

In a general solution, the definition of such rules must follow a good expressive model that allows to define the ability of each used server or proxy (server profiles). 

In order to be more general and flexible, it will be good to separate the matching algorithm and the capabilities of the server -such as the available translation methods, transcoding programs, etc. - which represent in fact one element of the content adaptation (other elements can be the client preferences, the network bandwidth, etc. - So, each server can have each proper adaptation methods (eg. English to French translator, WML to XHTML xslt style sheet, etc.), and the matching must ensure to make the best effort in providing adapted services without violating the presented constrains of each element (client, server, network, original content, etc. )





----------
Tayeb Lemlouma
http://www.inrialpes.fr/opera/people/Tayeb.Lemlouma/index.html
Opera project
National Research Institute in Computer Science and Control (INRIA Rhône-Alpes, France )
Office B213, phone (+33) 04 76 61 52 81, Fax (+33) 04 76 61 52 07.