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[ttml2] negative feature designators aren't future proof

From: Nigel Megitt via GitHub <sysbot+gh@w3.org>
Date: Tue, 13 Mar 2018 18:44:48 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-304889741-1520966687-sysbot+gh@w3.org>
nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:

== negative feature designators aren't future proof ==
The way that non-support inverse style feature designators like `#textEmphasis-no-color` and `#textEmphasis-no-quoted-string` are defined is open ended. Rather than requiring support for a specific subset of syntax+semantics, they require for support for everything except some syntax+semantic, in an open ended way.

This means that if in the future an additional syntax+semantic is added to the value set of `tts:textEmphasis`, then the meaning of those features would change by default.

It also presents a bit of a logic puzzle, to say the least, when interpreting `mostRestrictive` and `leastRestrictive` with respect to negative features.

To avoid this, I propose we refactor those features so that we only have positive definitions, i.e. support for a bounded set of syntax and semantics.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/697 using your GitHub account
Received on Tuesday, 13 March 2018 18:44:50 UTC

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