Prioritization of different typographic features

We can consider marking the importance of different typographic features in some way (kind of like the WCAG conformance levels), such as:

• Must-have features
• Important features
• Features only used in advanced publishing

I think this information is useful to spec writers, {browser, e-book reader, word processor, desktop publishing software} vendors, and content authors/developers alike, because they can refer to the importance levels to determine priorities when writing specs, implementing specs, and creating content using features in software.

Currently, some prioritization information can be seen in the Gap Analysis document, but it is gap-oriented and not instructive enough (for example, for a vendor trying to implement a new browser).

Here are a few example features:

Must-have features

• Support rendering of all Simplified Chinese and Traditional Chinese punctuations

Important features

• Increased inter-character spacing
• Support prohibition rules for line start and line end
• Support prohibition rules for unbreakable marks
• Extra spacing between adjacent Han characters and Western characters
• Support mixed text composition in vertical writing mode
• Support Bopomofo
• Support pinyin
• Paragraph adjustment
• Line adjustment

Features only used in advanced publishing

• Reduced inter-character spacing
• Punctuation width adjustment
• Support interlinear comments

Start with the Gap Analysis document and the linked sections covering punctuation, spacing, line breaking, vertical writing, Bopomofo, pinyin, and paragraph or line adjustment. Establish an agreed prioritization scheme, decide how it should be represented in the requirements, and apply it consistently to the relevant features.