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Non-prohibition of partially supported features. #488

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skynavga opened this issue Sep 24, 2019 · 6 comments · Fixed by #501
Closed

Non-prohibition of partially supported features. #488

skynavga opened this issue Sep 24, 2019 · 6 comments · Fixed by #501
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@palemieux
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for review imsc1.2
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IMSC1.2-CR

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@skynavga
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In §6 it is stated

All features specified in [ttml2] are prohibited unless specified otherwise below

however, there appears to be no prohibition against the use of features that are marked as partially supported.

For example, #base-version-2 includes support for #base-general, and §6 marks #base-version-2 as "partially supported via #base", but does not otherwise state that the underlying features of #base-version-2 that are not included in the underlying features of #base are prohibited.

The same comment applies to all other partially supported features.

If the intention is to prohibit underlying features not covered by statements of only partial support, then I would expect a general normative statement to be present that states something like:

If a feature or extension is marked as partially supported, then the vocabulary, syntax, and attribute values of the feature or extension that are not included in the statement of partial support are prohibited.

This text should probably go into §4 Conformance.
@skynavga
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I should add that, as presently defined in IMSC 1.1, a validator may interpret, for example,

<body xml:base=".">...</body>

as permitted (non-prohibited) in which case reporting this usage as invalid would be incorrect.

@skynavga
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Amending my above, I see that [TTML2] E.1.27 states:

It is an error for a content profile to require or permit use of the #base-version-2 feature but prohibit use of any of the following features: #base or #base-general.

So perhaps it is not possible to prohibit a subset of a partially supported feature without running afoul of [TTML2] which pretty much repeats the above for every compound feature definition.

@cconcolato
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I agree the current text can be confusing. I also think the intent is to prohibit the features that are not explicitly supported. I would agree with your proposal in your initial statement.

@palemieux
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So perhaps it is not possible to prohibit a subset of a partially supported feature without running afoul of [TTML2] which pretty much repeats the above for every compound feature definition.

@skynavga This is the reason why IMSC neither prohibit nor permits #base-version-2, but merely specifies the disposition of its subset features.

I suggest the note reads:

A feature or extension marked as partially supported is neither prohibited nor permitted. Instead, the disposition of each of its subset extension or feature is specified individually.

@palemieux palemieux self-assigned this Oct 10, 2019
palemieux added a commit that referenced this issue Oct 11, 2019
@palemieux
Clarify partially supported disposition (#488)
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@palemieux palemieux mentioned this issue Oct 11, 2019
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@palemieux palemieux removed the imsc1.1 label Oct 11, 2019
@palemieux palemieux added this to the IMSC1.2-WD2 milestone Oct 11, 2019
@palemieux palemieux mentioned this issue Oct 11, 2019
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@nigelmegitt
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I could live with either @skynavga 's original proposal or @palemieux 's modified one.

One thing I don't like about @palemieux's suggestion in #488 (comment) is that I do not know what state "neither prohibited nor permitted" defines - it seems to be impossible. From that perspective @skynavga 's proposal is clearer.

A simple tweak would be to change "neither prohibited nor permitted" to "neither completely prohibited nor completely permitted".

@palemieux
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A simple tweak would be to change "neither prohibited nor permitted" to "neither completely prohibited nor completely permitted".

+1

palemieux added a commit that referenced this issue Oct 15, 2019
@palemieux
Address #488 (comment)
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palemieux added a commit that referenced this issue Oct 29, 2019
@palemieux
Clarify partially supported disposition (#488)
d335896
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Clarify partially supported disposition w3c/imsc
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@skynavga @cconcolato @palemieux @nigelmegitt