Represent mixed numbers with structural fractions

[abcdsen-create]

Priority: High

Description

Document
that precomposed fraction characters such as ½, ⅓, and ¼ must not be used as the fractional
part of a mixed number. Use <mfrac> and join it to the whole number with
U+2064 INVISIBLE PLUS so the expression is recognized as one mixed number.

Recommended markup

<mn>1</mn><mo>&#x2064;</mo><mfrac><mn>1</mn><mn>4</mn></mfrac>

Acceptance criteria

• Guidance prohibits precomposed fraction glyphs for structural fractions.
• <mfrac> and U+2064 are documented.
• The example is verified to read as “one and a quarter,” or the language-appropriate equivalent.
• A validation or QA check can identify precomposed fraction characters inside <mn>.