Hi all,
As discussed recently, the current DIAL [1] has a dependency on XHTML 2.0, XFORMS etc. Whilst the value of these languages is well understood, it does tie DIAL to their roadmaps and means that Web developers have to change their markup accordingly. As such José and I have been looking at breaking out the content selection into a stylesheet, along the same 'seperation of concern' principles that CSS uses for style selection. This is also in line with a (very early) comment from Elliote Rusty Harold [2], that embedding the selection directives directly in the Web page contravenes web principles.
I've attached an example: content in XHTML 1 (an image and an adults-only link), plus an XLST which picks which format image to use and filters the adult link if the user is underage. For now, the parameters which determine the bandwidth of the request and the ability for the user to see adult links are hardcoded; with a standard Delivery Context API these could be evaluated at runtime by the browser in tandem with the delivery network.
(Note, you should be able to open example.htm in IE which will perform the XSLT for you. Not sure if that's the case for IE7 though).
I still believe that the existing DIAL has merit as an Enterprise/Content Management System language, the advantages being listed in the primer [3]. By allowing a 'lightweight' version as well we provide a standard to authors of existing web pages who want to vary content according to delivery context. This is another driver for a standard Delivery Context API.
Cheers,
Kevin
[1] http://www.w3.org/TR/dial/
[2] http://lists.w3.org/Archives/Member/w3c-di-wg/2006Oct/0089.html
[3] http://www.w3.org/TR/dial-primer/#intro-howdifferent
