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A name, a definition sign and alternatives.
Also known as: BNF rule, Production notation
The Backus-Naur Form notation for a production rule, defining a symbol in terms of others.
Defines a symbol in terms of other symbols in a formal grammar.
Contexts: Technical drawing, Software
Separates alternatives with a vertical bar, a convention that spread from grammar notation into regular expressions and command-line usage messages.
Contexts: Technical drawing, Software
A name in angle brackets, a definition sign of a colon and equals or an arrow, and a sequence of alternatives separated by vertical bars.
A fuller structured visual breakdown is not yet documented for this symbol.