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

[Giuseppe Bilotta <giuseppe.bilotta at gmail.com>]

On Sun, Aug 16, 2009 at 7:40 PM, Kristof
Zelechovski<giecrilj at stegny.2a.pl> wrote:
> An URI should not contain several other assorted URI.  URI are meant to be
> readable, as far as it is possible.

Collecting multiple URIs together does not necessarily make the URI
less readable. In fact, something like:

fallback:|image.png|image.gif

is way more readable than most data: URIs.

As for having a single URI act as collector for multiple URIs, I don't
really see what the big problem is. I cannot think of a better way to
provide multiple reference points in a standardized, uniform way. I'm
open to suggestions for alternatives, of course.

> As you have shown, it would be straightforward to use an attribute of type
> URI set instead.

It would be possible where, exactly? Even CSS3 itself does not offer
this possibility everywhere. For example, a place where it would be
_very_ important (the background-image property) does not allow the
specification of alternative sources, since the comma-separated list
of URIs has a different meaning in that case.

> I consider it a feature that markup languages are verbose.  The more concise
> the language, the harder it is to achieve interop.  If you find it to be an
> obstacle, you can just use a suitable code generator.

I have no problems with verbosity. The problem is the lack of a
significant feature. Neither HTML nor CSS, despite their verbosity,
provide a uniform, consistent way to define fallbacks for missing or
unsupported content. CSS3 has extremely limited support for fallbacks
with the content: property, HTML allows some nested-object hacks.
Neither solution is satisfactory, the CSS3 one due to its extremely
limited scope, the HTML one because it completely breaks meaningful
document handling.

The fallback scheme would provide a uniform, consistent way to define
fallbacks for missing and/or unsupported content, a mechanism that
would work in HTML, CSS, and any other context where URIs can be
specified.


> -----Original Message-----
> From: uri-review-bounces at ietf.org [mailto:uri-review-bounces at ietf.org] On
> Behalf Of Giuseppe Bilotta
> Sent: Saturday, August 15, 2009 9:21 PM
> To: uri-review at ietf.org
> Subject: [Uri-review] Proposal for a 'fallback' URI scheme
>
> Hello all,
>
> The need for such a fallback mechanism is also shown for example by
> the introduction in CSS3 content module draft of the syntax "content:
> url(someurl), url(someotherurl)" which is however CSS3-specific.
> Having something similar at a more generic level would allow the
> fallback mechanism to be used e.g. in HTML 'img' tags (or in the
> 'video' and 'audio' tag of the upcoming HTML5 specification).
>
>
>
>



-- 
Giuseppe "Oblomov" Bilotta