ExpressionOf

Customizing the metamodel > Using ListOf, OneOf, and ExpressionOf > ExpressionOf

ExpressionOf

ExpressionOf enables you to express references to objects using complex operators and delimiters. Usually, it is used to refer to data elements and data structures (DATA), it is not restricted to that use.

Syntax

References defined with ExpressionOf are entered in a dialog box using the syntax:

A + B + C

A +
B +
C

A
B
C

The elements can be written on one line or more than one line; the division between one element and the next is determined by white space. By convention, + (plus sign) is used to divide the individual data items, but it is not required.

Operators and delimiters

The following special operators and delimiters can be used in specifying expressions:

Symbol	Description
+	And (optional)
[...\|...]	Either-or
{...}	Iterations of
i{...}j	Allow from “i” to “j” iterations of
(...)	The enclosed component is optional
@	The component is a key field
@n	The component is the nth element of the elements making up a compound key
...	The enclosed text is a comment
/.../	The enclosed text is a comment but has significance to the Schema Generator

Sub-expressions can be nested within other expressions. For example, ITERATIONS OF can be included within EITHER OR brackets.

[ n1{...}n2 | n3{...}n4 ]

Example of EXPRESSIONOF listbox

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