Rules and triggers exist in a 3 level hierarchy:

                       DICTIONARY LEVEL
                             |
                             |
                             |
                         FILE LEVEL
                             |
                             |
                             |
                       PROCESS LEVEL

When working with a field at any level of the hierarchy you CANNOT VIOLATE a rule or trigger that exists at a higher level in the hierarchy.

The level in the hierarchy you are working at is easy to remember: