W3C home > Mailing lists > Public > public-html@w3.org > September 2007

Re: HDP: Revised "Support Existing Content" Principle

From: Maciej Stachowiak <mjs@apple.com>
Date: Mon, 17 Sep 2007 18:58:53 -0700
Cc: "public-html@w3.org WG" <public-html@w3.org>
Message-Id: <5AB03171-122B-433A-942E-A113D9682D22@apple.com>
To: Marghanita da Cruz <marghanita@ramin.com.au>

On Sep 17, 2007, at 6:21 PM, Marghanita da Cruz wrote:

> To me, handling of poor markup by browsers is an example of
> the "Degrade Gracefully" Principle rather than the
> support existing content principle.

That's not the intent of the principle. "Degrade Gracefully" says  
nothing about the interaction of existing markup with either new or  
old browsers. It's all about new documents authored to conform to  
HTML5 being able to work reasonably in pre-HTML5 browsers.

> After sending my email, I felt I should have added the broken html  
> seems a good example of the degrade gracefully principle.
> As I see it, Support existing content refers to features that may have
> been in HTML3.2 or 4.01 or XHTML etc. specifications but
> have been dropped in later ones.

The intent of "Support Existing Content" is that it's about actual  
existing *content*, not existing specifications. So it would not cover  
spec features that have never been used or implemented, but it would  
cover features that have never been in any spec and won't be  
considered conforming.

The "Support Existing Content" and "Degrade Gracefully" principles are  
mirror images of each other. The first is about old content in new  
browsers, and the second is about new content in old browsers.

> My tests with the w3c compliance indicates that the quotes are  
> required for a
> tick/greenlight on conformance with 4.01 however, browsers degrade  
> gracefully if
> they are not present.

I just tried with the W3C Validator and the following validates (note  
the unquoted attribute values on img):

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd 
<p><img alt=foo src=foo.jpg>

> I see the principles as relevant to the drafting of HTML5. So,  
> providing an
> example of the implications of dropping a feature could be useful.
> eg. if vspace or alt was dropped browsers would still need to  
> support this feature.

Well, we'd have to define what "dropped" means. Dropping them from the  
conforming language would be irrelevant to browser support. Dropping  
them from the supported language would mean, in these two particular  
cases, that browsers would still have to implement it but without a  
spec to go on.

Received on Tuesday, 18 September 2007 08:03:16 UTC

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