ID (Identifier) or LUID (Locally Unique Identifier)

Identifiers for declarations and blocks.

Syntax

ID: LETTER ALPHANUMERIC*

and

LUID: $ID

where

LETTER       = [a-z] or [A-Z] 
ALPHANUMERIC = [0-9] or LETTER or _

A LUID is unique in an operator.

An identifier must not belong to the lists of keywords and reserved words (Keywords ).