[ttml2] Widen schema data type for `tts:opacity` to avoid false negative schema errors.

skynavga has just created a new issue for https://github.com/w3c/ttml2:

== Widen schema data type for `tts:opacity` to avoid false negative schema errors. ==
As noted in [1][2], there is the possibility of a false negative during schema validation when a continuously animatable style property (attribute) is defined using a data type that would not match `<animation-value-list>`. Upon reviewing the current spec and schema, we have the following continuously animatable style properties and their value types:

```
backgroundColor - xs:string
border          - xs:string
color           - xs:string
disparity       - xs:string
luminanceGain   - xs:string
opacity         - xs:float
position        - xs:string
textEmphasis - xs:string
textOutline - xs:string
textShadow - xs:string
gain  - xs:string
pan  - xs:string
```

So, with the exception of `tts:opacity`, there is no problem with false negatives with `tt:animate`. To address this exception, I propose we widen the data type of `tts:opacity` in the schemas (but not spec) to use the type `xs:string`. This would be an editorial change.

[1] https://github.com/w3c/ttml2/pull/956#pullrequestreview-143131465
[2] https://github.com/w3c/ttml2/pull/956#issuecomment-410837114

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/974 using your GitHub account

Received on Monday, 6 August 2018 20:16:34 UTC