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Clarify what support for "presentation logic" means #1516
Description
The reading system spec has this high-level requirement for the package document:
[A Reading System] MUST honor all presentation logic expressed through the Package Document [EPUB-33] (e.g., the reading order, fallback chains, page progression direction and fixed layouts).
https://w3c.github.io/epub-specs/epub33/rs/#sec-package-rs-conformance
The inclusion of fixed layouts in the examples is confusing, though, as it there is a separate bullet for fixed layout handling in the same list.
I believe the intention of this bullet was only to require support for the "presentation logic" expressed directly through the elements and attributes of the package document, not indirectly through metadata expressed in meta tags.
On top of the general ambiguity about what "presentation logic" refers to, "honor" isn't exactly a technical term. The bullet seems more like an indirection to actual requirements/recommendations than something that can be tested.
In any case, it needs work.
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mattgarrish commentedon Apr 8, 2021
I think this "requirement" is just a regular old pointer wrapped up in some serious-sounding handwaving.
If there is "logic" that reading systems have to "honor", then it should be written as normative requirements not left for developers to vaguely give deference to.
Looking at the examples cited:
So what else is there? General rendering metadata is like fixed layouts - not really applicable but already covered.
If we're missing requirements for any of the above, or there's something I didn't spot, we should be adding those in not hoping they'll be "honored".
mattgarrish commentedon Apr 8, 2021
So, in case it needs saying, my proposal is to drop this statement/section.
iherman commentedon Apr 16, 2021
The issue was discussed in a meeting on 2021-04-15
List of resolutions:
View the transcript
6. What do we mean by support for "presentation logic"?
See github issue #1516.
Dave Cramer: we say RS must "honor presentation logic expressed through package document"
… mgarrish thinks we should just delete it since we already require all the pieces of that in other places in the RS spec
… making this statement redundant
Brady Duga: agree
Marisa DeMeglio: yes, agree