(1) Any of the following types of expressions: a) identifiers, b) parenthesized expressions, c) function calls, d) array element specifications, e) structure member specifications, or f) union member specifications.
(2) Literals, names, and names qualified by the :: (scope resolution) operator.
(3) The basic primitive structure of the XQuery language. Primary expressions include literals, variable references, context item expressions, constructors, and function calls. A primary expression can also be created by enclosing any expression in parentheses, which can help to control the precedence of operators.