Customizing the metamodel > Using ListOf, OneOf, and ExpressionOf > OneOf
  
OneOf
A OneOf list box creates a list box that enables the user to select one, and only one, of a list of objects (Diagrams, Symbols, or Definitions) of a certain type. The object type referenced must have been defined already in SAPROPS.CFG or at the top of the USRPROPS.TXT file.
Example
DEFINITION "Issue"
{
PROPERTY "Assigned To"
{ EDIT ONEOF "Risk" LENGTH 100 }
...
}
Example of ONEOF listbox
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Filtering the list of items
The list of items for a OneOf command can be filtered (similar to the ListOf list) by using filter keywords such as OF DEFINITION REFERENCED IN and OF DEFINITION AND SUPERS REFERENCED IN.
Heterogeneous oneof list
A typical OneOf statement provides a list of one object type. To create a OneOf list that references more than one object type, use the HETEROGENEOUS (ONEOF, LISTOF) keyword.
See also
Using ListOf, OneOf, and ExpressionOf