[ttml2] Clarify "considered an error" (#1067)

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

== Clarify "considered an error" ==
As discussed on today's call (w3c/ttwg#31) in the context of #1049, wherever a condition is described as "considered an error" without qualification of the processing context in which it is an error, this needs to be addressed.

For example, under tts:extent we have:

> All other syntactically legal values must not be used in this context, and, if used, must be considered an error for the purpose of validation processing and must be ignored for the purpose of presentation processing, in which case the initial value (auto) applies.

which is clear, whereas in other places such as under tts:rubyPosition, we have:

> If specified (on the former ruby text content), then it is considered an error, and must be ignored for the purpose of presentation processing.

There are currently 13 matches for "considered an error" in the spec, soon expected to be 14.

In all cases, it should be clear what the processor behaviour is if the incorrect usage occurs, for example:
* validation processor reports an error
* presentation processor either aborts or continues, and if continuing, what the error handling is, typically some syntax is ignored.

The fix for this should be forward-ported to TTML3 also.

If the fix results in normative changes then new or updated associated tests for validation processors and presentation processors may be needed, and are part of the fix for this issue.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/1067 using your GitHub account

Received on Thursday, 4 April 2019 16:59:40 UTC