Customizing the metamodel : Keywords for USRPROPS : LISTONLYCOMBO
  
LISTONLYCOMBO
Provides a drop-down list no matter how many LIST values there are. In addition, the user cannot type in their own values to the list.
The LISTONLYCOMBO keyword provides functionality that the LIST command does not – when using the LIST command, System Architect automatically displays a list as a list of checkbox choices if the number of values in the LIST statement is four or less. If the number of values is five or more, the list is automatically displayed as a drop-down list box. To have a drop-down list box but only have four or less LIST values, use the LISTONLYCOMBO keyword.
Example
List "Importance"
{
Value "Mandatory"
Value "Strongly Desired"
Value "Should Have"
}
Definition "Use Case Step"
{
PROPERTY "Importance" { EDIT TEXT LISTONLYCOMBO LIST "Importance" LENGTH 20 DEFAULT "Should Have"}
..}
In the example above, the list is provided in the Use Case Step definition dialog as a drop-down list even though there are only three values in the List statement. If you had used the simple LIST statement, then the values would have been shown as toggle boxes since there are less than five values.