<percentage> not defined

[nigelmegitt]

The new attribute ittp:activeArea takes 4 of <percentage> but this is not defined. One place it could potentially be derived from is a subset of the TTML1SE definition of <length> however that definition of percentage is based on number which permits negative values; in the case of ittp:activeArea negative values are prohibited.

Steps to resolve:

• Clarify source of definition of <percentage>.
• If it's from TTML1SE as above then add a normative statement prohibiting negative values.

[palemieux]

Clarify source of definition of .

The source of <percentage> has been clarified.

If it's from TTML1SE as above then add a normative statement prohibiting negative values.

The ittp:activeArea syntax definition specifies that the lengths are non-negative.

[nigelmegitt]

Thanks @palemieux that helps. I'm a bit unclear about the normative status of something with a syntax that looks like a code comment; I'm not sure if this is done elsewhere and if it is strong enough. I would prefer an explicit statement with a normative language keyword for the avoidance of any doubt.

[palemieux]

@nigelmegitt Constraints expressed in-band the syntax definition is used throughout TTML1 and IMSC1, see ttp:cellResolution and ittp:aspectRatio, for instance.

[nigelmegitt]

OK I'm not delighted by it, but am prepared to accept it.

[palemieux]

Closed by #209