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Re: semantic level of SVG usage

From: Cohn, Jonathan <jcohn@air.org>
Date: Wed, 17 Aug 2016 17:11:23 +0000
To: Rich Morin <rdm@cfcl.com>
CC: "w3c-wai-ig@w3.org" <w3c-wai-ig@w3.org>, www-svg <www-svg@w3.org>
Message-ID: <84025FC1-BAF3-4E97-9E1A-68AE86B1A6FA@air.org>
Is the labeling of SVG supported by the primary screen readers at this time? Would your proposal mean that all screen readers would need to implement a second approach to providing information? 

Jonathan Cohn
> On Aug 17, 2016, at 12:20 PM, Rich Morin <rdm@cfcl.com> wrote:
> Although I like the idea of adding ARIA metadata to SVG, I'm concerned
> that its effectiveness may be extremely limited by the semantic level
> of SVG tags and their typical usage.
> # Motivation
> Consider a data flow diagram, as produced by OmniGraffle. The building
> blocks of the diagram are geometric shapes and arrows, but this level
> of abstraction is largely absent from the SVG.  Instead, it uses either
> a filled `path` or a pair of `rect` elements.
> And, although the semantic payload of the diagram is largely concerned
> with connectivity, the SVG contains no information on this.  The only
> way I can see to get connectivity information is to compare locations
> of line endpoints with the (fuzzy) boundaries of geometric shapes.
> I have similar concerns about other kinds of plots and diagrams.  For
> example, the semantic payload of a pie chart or a histogram has to do
> with the numeric quantities being represented, not with the angles or
> heights used in the generated image.
> The SVG images produced by D3.js are even more problematic, using tags
> which have only a distant relationship to the semantic payload:
>  https://github.com/d3/d3/wiki/gallery

>  http://bl.ocks.org/mbostock

> In summary, adding attributes to SVG tags may not be enough to make
> the resulting image particularly accessible.
> # Proposal
> By combining SVG attributes (e.g., object identity) with a separate
> section of the XML document, it would be possible to add arbitrary
> semantic information to the image.  For example, the added section
> could describe graph connectivity, encode raw data for plots, etc.
> This could support a variety of post-processing needs, ranging from
> accessibility to machine learning.  And, because the added section
> wouldn't be part of the base SVG, programs could simply ignore it.
> Comments and suggestions welcome.
> -r
> P.S.  Amanda Lacy, Johannes Rössel, and Gene Dronek contributed
>      valuable information and insights to this note, but they
>      are not responsible for my conclusions.
> -- 
> http://www.cfcl.com/rdm           Rich Morin           rdm@cfcl.com
> http://www.cfcl.com/rdm/resume    San Bruno, CA, USA   +1 650-873-7841
> Software system design, development, and documentation

Received on Wednesday, 17 August 2016 17:11:50 UTC

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