we might up end up with exposing these as object attributes only, which makes this bug wfm. See Jamie's edge case description of non continuous ARIA grids . Here's a newer discussion of the problem which is in progress still .  https://lists.linuxfoundation.org/pipermail/accessibility-ia2/2015-June/001913.html  https://lists.w3.org/Archives/Public/public-aria/2016Aug/0064.html
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