public function describe( $expressions /* expressions ... */ ) {
		$expressions = is_array( $expressions ) ? $expressions : func_get_args();

		$this->setQueryForm( 'DESCRIBE' );
		$this->addExpressions(
			$expressions,
			ExpressionValidator::VALIDATE_VARIABLE | ExpressionValidator::VALIDATE_FUNCTION_AS
				| ExpressionValidator::VALIDATE_IRI | ExpressionValidator::VALIDATE_PREFIXED_IRI
		);

		return $this;
	}