As more experience is gathered in implementing the characters, adjustments in the properties may become necessary. However, character properties will not be changed in a way that would affect character identity. The Bidi Category values will not be further subdivided. Combining classes are limited to the values 0 to 255. Canonical and Compatibility mappings are always in canonical order, and the resulting recursive decomposition will also be in canonical order.
Canonical mappings are always limited either to a single value or to a pair.
The second character in the pair cannot itself have a canonical mapping.