Consider two FileMaker Pro 8 files, Alpha and Beta, where a table from Beta appears...

Layouts in Alpha can display data from Beta.

Alpha can contain multiple valid file references to Beta.

It is impossible to lock records in both Alpha and Beta simultaneously.

Layouts from Beta cannot be displayed in the same window as layouts from Alpha.

A table occurrence from Beta is required on Alpha's Relationships Graph in order to call a script in Beta from Alpha.