Let´s take the Specifications´model. The predefined relations are shown in the picture, yet, cascading has not been enabled for deletions in the SQL server for the corresponding relations. Then, you need to make sure that, when removing a specification, all its SpecificationHeaders have been removed first. Of course, each and every SpecificationHeader must have been cleared off its SpecificationItems prior to its own removal.
Here is some code to do that: