ID Compat Math Start

ID Compat Math Start is a character property that identifies characters which can serve as the starting point of a mathematical identifier in contexts where compatibility with other standards, such as those for programming languages or mathematical markup, is required. These characters include letters, digits, and certain symbols that are considered acceptable for beginning a mathematical variable or function name, even if they are not strictly mathematical alphanumeric symbols. The property ensures that identifiers beginning with such characters remain interoperable across different systems, allowing for consistent parsing and rendering of mathematical expressions. It complements related properties that define the continuation or middle characters of such identifiers, together forming a complete set of rules for constructing valid mathematical names.