When to include the "foreignKey" attribute in ds.xml file?

[Blama]

Hi Isomorphic,

I have this structure in a RDBMS:

person(id: int, honorific_id: int, givenname: varchar, name: varchar)
honorific(id: int, shortdesc: varchar, longdesc: varchar), DB-level FK is set.

Do you suggest / is it necessary to set the foreignKey-attribute in .ds.xml?

From my reading of the javadocs it is necessary/helpful for:
- Update of cached entries (eg. 2nd grid for editing "honorific"-data, display of new added data in "person"-honorific-Dropdown without reload).
- DataBoundComponent: Drag and Drop.
- DataBoundComponent: DropValues.

NOT necessary/helpful in my example case, as:
1) display of names instead of honorific_ids via fetch-operation binding with join and different displayField="..." in ds.xml for the honorific_id
2) display of editor-Dropdown (ComboBoxItem) with optionDataSource in java file
3) display of filter-Dropdown (SelectItem) with optionDataSource in java file.

Could you advise if this is correct / add other cases? Or is it in general a good idea to include DB-level FKs in .ds.xml files as well?

Thank you,
Blama