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Re: PDFs and NVDA


From: Karlen Communications
Date: Aug 21, 2011 3:30PM

I wrote an article on the Karlen Communications blog called "Headings, Headers, Headaches" to help explain the difference between heading styles, page headers and table headers...hence the "headache" part when you are learning the differences.


Cheers, Karen

Out of Office, Sent from my iPad

On 2011-08-21, at 4:57 PM, "Bevi Chagnon" < <EMAIL REMOVED> > wrote:

> Lisa, I think you mean "headings" not "headers."
> They are very different parts of a page.
> To help understand the difference: when you think of a header also think of
> its mate, a footer. Headers are running headers (aka page numbers, folios,
> repeating info) that repeat at the top of every page.
> A heading is a headline, subhead, title or something similar that is part of
> the body text on a page. Headings are used by assistive technologies for
> quick navigation while headers are usually ignored.
> Similar usage for tables. A table header is the repeating information at the
> top and includes the column heads. A table heading falls in within the body
> of the table and acts like a subhead, dividing one portion of a table from
> another.
> In tables, the header is used by assistive technologies to orientate the
> user, while table headings (subheads) are usually read like any other text
> in the table and often confuse the heck out of AT users.
> --Bevi Chagnon
> (former editor and typesetting)
> --
> Bevi Chagnon | <EMAIL REMOVED>
> PubCom - Trainers, consultants, designers, and developers
> Print, Web, Acrobat, XML, eBooks, and Federal Section 508
> --
> * It's our 30th Year! *
> -----Original Message-----
> [mailto: <EMAIL REMOVED> ] On Behalf Of LSnider
> Sent: Sunday, August 21, 2011 3:24 PM
> To: WebAIM Discussion List
> Subject: Re: [WebAIM] PDFs and NVDA
> Hi Duff,
> Thanks for your answers, much appreciated. So a few follow up questions:
> -If most people use the tagged reading order, what are the uses for the
> other reading orders in Acrobat/Reader?
> -If I don't use proper headers in a Word doc (which will be made into the
> PDF), the tagging can't tell what is a header, correct? It just guesses? To
> me with my testing, it seems like it guesses and I think that is what you
> said below, but just wanted to confirm.
> -The touchup reading order in Acrobat can be used to tweak what the tagging
> does? I haven't used that one a lot before...I usually try to make well
> structured documents in Word and they usually come out okay, but maybe I
> should be using that touchup tool..
> Thanks again, this is very helpful.
> Cheers
> Lisa
> On Sun, Aug 21, 2011 at 11:26 AM, Duff Johnson < <EMAIL REMOVED> >wrote:
>> Yes. Heading structure may be found in the tags. In PDF, there's no
>> other proper place to look for it (I'm leaving aside a technically
>> available but nonetheless pointless option).
>> Since tags are the only place in which to find the file's logical
>> structure (sequence, nesting and semantics), yes, you need
>> Acrobat/Reader/3rd party option to use the "tagged reading order".
>> Tags are essential to accessible PDF, period. The only exception (in a
>> purely operational sense) would be a document that is so simple that
>> it's possible to have the raw print stream (thanks Karen!) just happen
>> to match the document's logical structure.
>> As such, there is no "rule' about what to do in the absence of tags -
>> there are merely a couple of options, both of them bad.
>> In the case of an untagged PDF, applications can either (a) follow the
>> raw print stream or (b) possess the smarts to analyze the page layout
>> and make choices that override the as-printed sequence.
>> An untagged PDF - even if all the content just happens to occur in
>> correct reading order - is semantically equivalent to a single giant
>> <P> tag containing all the text in the PDF - unacceptable for
>> accessibility purposes.
>> I hope this helps.
>> Duff Johnson