RE: AccessModeSufficient

Hi John,

 

It’s easier to think of accessMode as an array and accessModeSufficient as an array of arrays. The problem with EPUB is it can’t represent complex metadata and HTML really isn’t any better.

 

So with accessMode, you’re identifying all the ways that content is represented by default. The recommended practice is to put only one value per metadata element. So if you have:

 

<meta property=”schema:accessMode”>textual</meta>

<meta property=”schema:accessMode”>visual</meta>

 

for a book composed of text and images, the result should be an array of all the values. Since you can’t do proper arrays in EPUB or HTML, that means the closest single-element equivalent would be:

 

<meta property=”schema:accessMode”>textual,visual</meta>

 

But then you rely on the user agent processing the values as a comma separated list and not a plain text string.

 

If we had JSON at our disposal, for example, the more accurate way to express the metadata would be:

 

“schema:accessMode”: [“textual”, “visual”]

 

The accessModeSufficient property represents ways in which users can read the content, which is why it’s arrays of arrays. So when you have:

 

<meta property=”schema:accessModeSufficient”>textual,visual</meta>

<meta property=”schema:accessModeSufficient”>visual</meta>

 

What this would properly combine to, using JSON again, is:

 

“schema:accessModeSufficient”: [

              [“textual”, “visual”],

              [“textual”]

]

 

One pathway is being able to visually read the text and images while a second pathway has the information available in textual form alone (e.g., allowing TTS).

 

You don’t create a single array by taking a union of the values, otherwise you lose all information about what pathways are available to the user. But without being able to express arrays, we had to resort to using a comma-separated syntax for each list of values for this property. It’s hacky, but that’s not surprising for EPUB.

 

Hope this helps,

 

Matt

 

From: John Foliot <john@foliot.ca> 
Sent: May 5, 2022 10:57 AM
To: public-epub-wg@w3.org
Subject: AccessModeSufficient

 

Hello All,

 

I am struggling a bit with this metadata declaration, or more specifically the authoring pattern.  The examples shown at: http://kb.daisy.org/publishing/docs/metadata/schema.org/accessModeSufficient.html are a bit confusing to the uninitiated, but I believe I am understanding this correctly. Can I test that assumption?




As I understand it today, both meta values (AccessMode & AccessModeSufficient) can be expressed in one of two ways: each Mode value expressed on its own line as a separate entry, OR as a single metadata declaration with a comma separated list of values. (This is where the Daisy examples get a bit confusing.)

As I understand it then, this means that for the user-agent, this: 
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual</meta>
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">visual</meta>

and this: 
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual, visual</meta>

...are processed identically (that somehow the user-agent consuming the metadata is 'concatenating' the single value declarations programmatically, or accepting the author's concatenated declaration).

This also suggests then that this: 
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual, visual</meta>
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">auditory</meta>

…could be (would be?) processed the same as: 
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual, visual, auditory</meta> 

Is that correct? That if, in my metadata block, I make two accessModeSufficient declarations, one a comma separated list followed immediately by another declaration with a single 'third' (or fourth but different) value, that the user-agent will still process it as a concatenated list of all values in practice? Additionally (and perhaps conversely), is the concept of cascading in play here? By that I mean, if the metadata block states: 
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual, visual</meta>
      <meta xmlns:html=" <http://www.w3.org/1999/xhtml> http://www.w3.org/1999/xhtml " property="schema:accessModeSufficient">textual</meta> 
(This is an actual example on the Daisy page: Example 1 — EPUB 3)

... is it suggesting that the second declaration, without the second value of visual, "removes" or otherwise "erases" or overrides the previous declaration: first declaration = textual and visual, second declaration = textual; which may mean that 'visual' is no longer required (using a mechanism similar to CSS cascading)? Or is it that textual is redundantly declared a second time? (That is what is unclear in the Daisy KB entry I referenced.) Thanks in advance for the clarification(s).

JF

-- 

John Foliot | 
Senior Industry Specialist, Digital Accessibility | 
W3C Accessibility Standards Contributor |

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