BNF (Backus-Naur Form)

This was originally developed by J.Backus and P.Naur for Algol 60.

• a production (or rule) consists of a left-hand-side and a right-hand-side.
• The left-hand-side is a single non-terminal.
• The right-hand-side contains terminals and non-terminals, we use
  • We use | for alternatives.
  • We use juxtaposition for concatenation.
  • concatenation binds stronger than |.

• We often use quotes for terminals.
• We will usually distinguish terminals which are not quoted and non-terminals by capitalization.