hey all are created for different purpose. Please don't get confused with each other.
ACL - Purpose of this is to ensure what data users can access and how they can access it
Client Script - This is for Client side (or browser side) validation. Client side validation includes, making a field mandatory, read-only, hidden etc. This will get applied only at the browser.
UI Policy - This is similar to Client Script, except that not need to write a script.
CS>UI --> Client script runs first and UI policy after
Business Rule. This script runs at the server side when a form Insert, Update etc. This can do some action that can be achieved only by running from Server.
Field State (Mandatory,Visible, Read only) is generally applied in the following order of preference, where one is the top preference:
ACL (Visible/Disabled) Dictionary Entry (Mandatory/Disabled) UI Policy (Mandatory/Visible/Disabled) Data Policy as UI (Mandatory/Disabled) Client Script (Mandatory/Visible/Disabled)
Examples:
If the user does not have write access to a field (ACL), a UI Policy to make it editable will do nothing.
If a field is set to disabled on a Dictionary Entry, a UI Policy to make it mandatory or editable disabled will do nothing.
If a field is made read only by a Client Script, a UI Policy to make it editable will take preference.
3,4 or 5 may be variable based on order.
Execution order of scripts and engines
The order of execution is as follows:
Beforebusiness rules: Scripts configured to execute before the database operation with an order less than 1000.
Beforeengines. The following are not executed in any specific order:
Approval engine (for task and sys_approval_approver tables)
Assignment rules engine (for task tables)
Data policy engine
Escalation engine
Field normalization engine
Role engine - keeps role changes in sync with sys_user_has_role table (for sys_user, sys_user_group, sys_user_grmember, and sys_user_role tables)
Execution plan engine (for task tables)
Update version engine - creates version entry when sys_update_xml entry is written (for sys_update_xml table)
Data lookup engine inserts or updates
Workflow engine (for default workflows)
Beforebusiness rules: Scripts configured to execute before the database operation with an order greater than or equal to 1000.
The data base operation (insert, update, delete).
Afterbusiness rules: Scripts configured to execute after the database operation with an order less than 1000.
Afterengines. The following are not executed in any specific order:
Label engine
Listener engine
Table notifications engine
Role engine - keeps role changes in sync with sys_user_has_role table (for sys_user, sys_user_group, sys_user_grmember and sys_user_role tables)
Text indexing engine
Update sync engine
Workflow engine (for deferred workflows)
Trigger engine (for allFlow Designerflows)
Email notifications. The following are executed based on the weight of the notification record:
Notifications sent on an insert, update, or delete
Event-based notifications
Afterbusiness rules (Only active records). Scripts configured to execute after the database operation with an order greater than or equal to 1000.
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Thanks and Regards Ravi Gaurav | ServiceNow MVP 2025,2024 | ServiceNow Practice Lead | Solution Architect CGI M.Tech in Data Science & AI
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