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Re: Question about forward and backward compatibility

From: Jim Ley <jim@jibbering.com>
Date: Tue, 14 Dec 2004 20:18:56 -0000
To: www-svg@w3.org
Message-ID: <cpnhrq$m8l$1@sea.gmane.org>


"Robert O'Callahan" <rocallahan@gmail.com> wrote in message 
news:11e3066004120709151d7e81a4@mail.gmail.com...
> 1) Is there a way for authors to write a single SVG file that will
> take advantage of SVG 1.2 features but degrade gracefully in a user
> agent supporting only 1.1? It appears not, since the 1.1 user agent is
> required to visually show error due to the presence of 1.2-specific
> elements and attributes.

There is, you could switch on appropriate requiredFeatures couldn't you? 
no-one's going to actually do it though.  The problem here is that SVG 
1.0/1.1 didn't go down the "must ignore" good practice of the proposed TAG 
finding on this, but chose must reject, must reject is I think completely 
incompatible with the approach of SVG 1.2, which as you note makes it near 
impossible for a great many 1.2 documents to be processed by a 1.1 user 
agent.

If we can't get the 1.2 specification changed to be better (new namespace 
etc.) or we can't go down the CSS 2.1 approach and change the behaviour of 
1.0 or 1.1, the practical thing to do will be to ignore the visually show 
error if there's a version="1.2" and instead provide information in a status 
bar or similar that you have done this.  Or you could cease processing 1.2 
content and hand it off to another application.  This is one of the reasons 
I want an application/svg+xml mime-type which can help in these situations 
if it's defined such that only documents in 1.2 with scripting or similar 
should be delivered with that mime-type.  I think there is sufficient 
difference between the 2 sorts of documents.

Cheers,

Jim. 
Received on Tuesday, 14 December 2004 20:19:16 GMT

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