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Re: SVGT 1.2: Appendix C3: SVG Error Processing

From: Jim Ley <jim@jibbering.com>
Date: Mon, 2 Jan 2006 10:45:02 -0000
Message-ID: <007e01c60f89$97eb8a50$2402a8c0@Snufkin>
To: <www-svg@w3.org>

"Maciej Stachowiak" <mjs@apple.com>
>> Specifying error recovery does nothing to solve the decision of new  user 
>> agents deciding to ape the bugs and features of dominant UAs.
>
> If error recovery is not specified, then some particular weird way of 
> doing it is not a bug, it is a design choice. It's a lot harder to 
> convince someone to change their design choices than to convince them  to 
> rectify a bug against a particular spec.

The document is in error, that's a fact, if you feel a specification is 
going to convince someone then "this document is in error" is enough of a 
fact that it should convince them.

If the spec says "if you write this" "this happens" then it is much harder 
to argue the document is in error at all, it uses a feature from the spec to 
achieve a desired rendering, baking in the behaviour for ever more.

> I don't think you have presented a convincing counter-argument to the 
> experience of HTML, and the contrasting experiences of CSS and XML.

Yes, HTML has been a great success, XML a failure at the user level!  CSS 
was a failure such that a whole new good specification has been created - 
the fact that creating the good specification was possible is because of 
undefined error parsing.

> Having done a fair amount of work on a mainstream web browser, I know 
> that HTML is much harder to parse than CSS or XML as a result.

Of course, but that is because you are deciding to render invalid content, 
that is a choice, a choice I would always encourage, however your conclusion 
that specifying rendering behaviour in every single error condition would be 
of any help is incorrect.

I would absolutely encourage interopable error handling, I would encourage 
all UA developers to sit down and work out an agreement - write it up as an 
SVG Note whatever (I suggested a forum for discussion and a wiki previously 
http://svg.jibbering.com/svg/2005-12-28.html#T23-38-35 ) , it just shouldn't 
be part of the specification.

Error recovery is an inexact science, making it exact and preventing user 
agent choice stops user agents picking better error recovery.  It also means 
documents can no longer be in effect in error, meaning even user agents 
which aren't interested in interoperating with a previous UA have to 
implement a huge array of error recovery features, that they don't want to 
implement.

Jim. 
Received on Monday, 2 January 2006 10:45:29 GMT

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