Re: [Uri-review] Proposal for a 'fallback' URI scheme

[Toby A Inkster <mail at tobyinkster.co.uk>]

On 15 Aug 2009, at 20:21, Giuseppe Bilotta wrote:

> fallback:|somefile.svg|somefile.mng|somefile.png
>
> A supporting agent would then load the SVG file, or fall back to MNG
> if SVG is not supported, and finally to PNG if neither of the previous
> is supported.

This seems fairly unnecessary to me.

Firstly, (X)HTML already provides fallbacks for the OBJECT element.  
The fallbacks in your example could be written as:

	<object data="somefile.svg">
	  <object data="somefile.mng">
	    <img src="somefile.png" alt="some sensible text" />
	  </object>
	</object>

Secondly, HTTP connection negotiation already allows browsers to tell  
servers a specific list of content types they accept, and servers to  
deliver a file based on that information.

Thirdly, both the above techniques are already supported in existing,  
real-life browsers. A hypothetical "fallback:" URL scheme would not  
work in existing browsers, only being supported by shiny new browsers  
that were released after the fallback scheme was standardised. Thus  
anyone caring about backwards compatibility with older browsers (and  
surely backwards compatibility with older user agents is the entire  
point of providing fallbacks) would not use the scheme.

--
Toby A Inkster
<mailto:mail at tobyinkster.co.uk>
<http://tobyinkster.co.uk>