The semantics of a character are determined by its identity, normative properties, and behavior.

• Some normative behaviour is default behavior; this behaviour can be overridden by higher-level protocols. However, in the absence of such protocols, the behaviour must be observed so as to follow the character semantics.
• The character combination properties and the canonical ordering behaviour cannot be overridden by higher-level protocols. The purpose of this constraint is to guarantee that the order of combining marks in text and the results of normalisation are predictable.