Your customer is complaining that Service Desk users keep accidentally assigning Incidents to the Network CAB, instead of Network Support You have…

The Assignment group field is inherited by the Incident table from the parent Task table. To modify the behavior of an inherited field for a specific child table (in this case, Incident), the standard best practice is to use a Dictionary Override. By creating a Dictionary Override for the assignmentgroup field on the Incident table, you can apply a specific Reference Qualifier. This qualifier will filter the selectable groups to only include those with the type 'incident', effectively hiding the 'Network CAB' group and preventing incorrect assignments without altering the field's behavior on other task types.

A. A UI Action creates a button, link, or context menu item; it cannot be used to dynamically filter the records available in a reference field's lookup list.

B. While validation is possible, a UI Action is the wrong tool. This approach is also reactive (error after selection) rather than proactive (preventing the selection).

D. The Assignment Group field is a reference field to the sysusergroup table. It is not a choice field, so modifying a choice list is not applicable.

1. ServiceNow Product Documentation - Dictionary Overrides: "A dictionary override changes the properties of a field on an extended table... For example

you can override the reference qualifier on the task.assignmentgroup field for just the incident table." This directly supports using a Dictionary Override to apply a specific Reference Qualifier for the Incident table. (ServiceNow

Now Platform Administration

"Dictionary overrides").

2. ServiceNow Product Documentation - Reference Qualifiers: "Reference qualifiers restrict the data that is returned for a reference field." This confirms that a reference qualifier is the correct mechanism to filter the list of groups. The solution would involve adding a qualifier like typeLIKEincident to the Dictionary Override. (ServiceNow

Now Platform Administration

"Reference qualifiers").

3. ServiceNow Developer Training - Application Development Fundamentals: The courseware explains the concept of table extension and how child tables inherit fields from parent tables. It specifies that to alter an inherited field's attributes

such as a reference qualifier

for a single child table without affecting the parent or other child tables

a dictionary override must be used. (ServiceNow Developer Program

"Application Development Fundamentals" course materials

Module on Data Model).