19.514 style:rfc-language-tag - augments and other issues, see description

Reads:

The style:rfc-language-tag attribute augments the fo:language, fo:script and fo:country attributes. It shall only be used if its value could not be expressed as a valid combination of those. The value shall be a language identifier according to the rules of [RFC5646], or its successors. If a fall-back is provided for consumers that do not support the style:rfc-language-tag attribute, producers should add fo:language, fo:script and fo:country attributes whose values are as close as possible to the actual value of the style:rfc-language-tag attribute. Producers shall not use values for these attributes that contradict the value of the style:rfc-language-tag attribute.

Issues:

1) What does augment mean? Not to mention this isn't the form we use for other attribute definitions.

2) Close as possible? Have already said it can't be expressed so how do we measure close as possible?

3) Ditto for "shall not contradict". If I can't specify it, how can I contradict it?

Suggest:

"The number:rfc-language-tag attribute specifies a language identifier according to the rules of [RFC5646], or its successors.

It shall only be used if its value can not be expressed as a valid combination of the fo:language, fo:script and fo:country attributes.

Producers may add support for consumers that don't support the number:rfc-language-tag attribute by specifying fo:language, fo:script and fo:country attributes with values that are implementation dependent."