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Re: PDF accessibility guidelines. WAS: Re: PDF's and Signatures

From: Duff Johnson <duff@duff-johnson.com>
Date: Mon, 26 Jan 2015 10:38:18 -0500
Message-Id: <6CA8C09B-A0AB-4A2D-9AA2-BFB083715E96@duff-johnson.com>
To: WAI Interest Group <w3c-wai-ig@w3.org>
Hi Bob,

> the simple basic fact is that a pdf is a "photo" or "image" of a document

A PDF is not a “photo or an image” of a document. A PDF is a rendering of a source document generated at a particular moment in time.

Yes, content in PDF files is “fixed” in the sense that rendering of text and graphical content on a page is fully determined. In end-user parlance this feature is called “reliability”, or more precisely, “reliability in rendering”.

Much of HTML development is also obsessed with reliability in rendering. No-one thinks it’s great when Chrome, Safari, FireFox, IE, etc. can’t agree on how to display / operate a web page, right?

The big difference is that with PDF the reliability is baked into the file itself rather than being something the software has to determine.

> and no matter what is shown it is still treated or should be treated the same as any other image in a document.

What of the paragraphs, tables, lists, headings, annotations, photos, form-fields, etc. etc. in the PDF? Don’t they deserve semantic structures?

In HTML you have a nice situation where the content is inherently contained in semantic structures. In PDF, content is just… content. Semantic structures are applied to the content using tags. There are good things (flexibility) and bad things (complexity) about this model… but it’s certainly not “an image”.

Duff.
Received on Monday, 26 January 2015 15:38:48 UTC

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