Add @ttm:alt as shorthand for ttm:item name="altText" (#490). #506
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Built version can be found at https://rawgit.com/w3c/ttml2/issue-0490-add-ttm-alt-build/index.html |
spec/ttml2.xml
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| <div3 id="metadata-attribute-alt"> | ||
| <head>ttm:alt</head> | ||
| <p>The <att>ttm:alt</att> attribute serves as a shorthand expression for an equivalent |
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Do we need to state that the applicable xml:lang on the element applies, and that xml:space is considered to be "preserve" on attribute values?
Also probably worth noting that if these values need to be set explicitly, or indeed any other attribute on an ttm:item name="altText" then the element form needs to be used.
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sounds reasonable, will add
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@palemieux I don't agree that the altText attribute prose must match IMSC 1.0.1 ittm:altText, because a) it can't - see #490 (comment) and b) it is reasonable for TTML2 to be more general and for profiles to be more specific. Any modifications that are worth making to align the TTML2 structure with the IMSC one, such as usage notes, would need to be made on the |
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@palemieux regarding
I presume you are asking for a distinct feature for |
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@palemieux see 69867ff |
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@nigelmegitt added schema update and note/prose on lang/space |
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@palemieux are your comments addressed? |
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To address @palemieux, maybe we could add some text to "14.3.2 " in the "altText" part, not in the new attribute section. What seems to be missing are:
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@cconcolato in general, I am opposed to enumerating or describing applications of a feature, particularly when it is a feature that has a long history of various applications. also, what do you mean by "and the NOTE"? |
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I was talking about the NOTE in IMSC which talks about how it is different from HTML5. |
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That note is irrelevant to TTML (and IMSC for that matter), and adds nothing that clarifies or explains TTML metadata semantics. If we went down this path, we would need notes explaining that TTML {head,body,div,p,span,br} are distinct from HTML vocabulary of the same name. |
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In preparation for the F2F meeting, below is a summary of my objection.
This PR, which (i) proposes to introduce
Assuming there is a desire to preserve the altText element, I think the simplest path forward is to:
Alternatively, IMSC 1.1 could continue supporting |
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On Tue, Jan 2, 2018 at 3:49 PM, Pierre-Anthony Lemieux < ***@***.***> wrote:
In preparation for the F2F meeting, below is a summary of my objection.
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IMSC1 introduced ittm:altText. The prose around ittm:altText was
subject of much discussion, including the note at the end of 7.7.4 and the
MAY in the introductory paragraph.
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TTML2 eventually introduced <ttm:item name="altText"/> to serve a
similar purpose. [ed.: it is still not clear to me what motivated using a
generic ttm:item element plus @name, instead of simply introducing
individual elements, i.e. using native XML extension mechanisms.]
The reason ttm:item was introduced was to avoid defining new attributes
over time, but instead, have a generic mechanism that would serve to
support all future items that might have been specified as attributes.
- the discussion at the TTWG F2F pointed towards using an @ttm:alt
attribute instead of <ttm:item name="altText"/>.
I do not agree with this characterization, in particular, your use of
"instead of". At the time, I clearly recall saying it would be a shorthand
for the existing ttm:item form.
This PR, which (i) proposes to introduce @ttm:alt *in addition* to <ttm:item
name="altText"/> and (ii) does not match IMSC1 prose, has the following
pitfalls:
- supporting both @ttm:alt and <ttm:item name="altText"/> complicates
implementations, especially since the mapping is not one-to-one
actually, it is one-to-one (injective), in both directions, but it is not
onto (surjective), from ttm:alt to ttm:item
- both @ttm:alt and <ttm:item name="altText"/> diverge syntactically
from ittm:altText
there is no (agreed) requirement that TTML2 incorporate IMSC1.0 features
while maintaining exact syntax or prose; the requirement is to support
equivalent functionality, which ttm:alt and its longhand form do
- additional prose will be required in IMSC1.1 to backfill any prose
absent from TTML2, and constrain out <ttm:item name="altText"/>,
thereby somewhat defeating the purpose of IMSC1.1 referencing TTML2
- the new prose in both TTML2 and IMSC1.1 may yield new comments
whereas the prose in IMSC1 is presumably acceptable
it is not acceptable to Skynav, e.g., the note referencing HTML is not
acceptable, nor is the
Assuming there is a desire to preserve the altText element, I think the
simplest path forward is to:
- move ittm:altText to the TTML2 namespace (as ttm:altText)
Skynav would object to this due to (1) there being (1) no (agreed)
requirement to incorporate this syntax directly, and (2) the extra four
characters required by the name altText as opposed to alt. The reason this
was proposed was to provide a shorthand: adopting a "middlehand" between a
reasonable shorthand (ttm:alt) and its stated longhand obviates the purpose
of this process.
- deprecate ittm:altText in IMSC 1.1
- use ttm:altText in IMSC 1.1
Alternatively, IMSC 1.1 could continue supporting ittm:altText,
regardless of what TTML2 does.
The simplest solution in my thinking is for IMSC1.1 to adopt ttm:alt and
also continue supporting ittm:altText.
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WG resolves not to merge this and not to add the ttm:altText attribute. See the issue. |
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Per #490 (comment), have resolved not to add |
Closes #490.