W3C home > Mailing lists > Public > public-html@w3.org > January 2010

Re: Understanding the "applicable specifications" clause (was: Re: Decentralised extensibility idea (ISSUE-41))

From: David Singer <singer@apple.com>
Date: Thu, 21 Jan 2010 10:09:25 +0900
Message-Id: <58B3A83B-F557-487F-8E50-3C9A3E3FCE19@apple.com>
To: HTML WG <public-html@w3.org>
This may be an aside, but...

On Jan 20, 2010, at 19:35 , Lachlan Hunt wrote:
> This can occur because HTML5 doesn't define any way for documents to declare what they conform to, which is by design.  Previous editions of HTML allowed authors to explicitly associate their documents with custom DTDs which provided limited means by which a document could declare and be machine-checked against some additional conformance requirements, but this approach has been, and should remain, abandoned.

The MP4 file format specification handles this with a simple list of code-points that identify the specifications which the author claims conformance to.  This can be useful (for a start, if a reader doesn't implement any of the identified specs, then it has a big warning that it might not understand the document).  Having a list makes it possible to revise specifications, or identify restricted versions.  For example, "I claim conformance to BasicFormat 1.0, BasicFormat 1.1, and PortableRestrictedFormat 1.0" enables a 'old' general reader implementing BasicFormat 1.0 to go ahead, as well as a portable reader that needs to know whether the document conforms to the restrictions.

This is a long way from identifying schemas (which is both too detailed, and too weak a statement).

I am somewhat of a fan of this;  it replaces the question "what is this document?" with "what specifications does this document conform to?" which is more useful, IMHO.  Until you need to decide which (singular) file extension and MIME type it gets :-(

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Thursday, 21 January 2010 01:09:59 UTC

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