Foreign Data Providers (FDP) is the total number of external components (or classes) from which foreign attributes are accessed. Here, these external classes are provisioning data. Ideally, all of the data should be locally available within the class to promote cohesion.
Consider method ‘M’ in class ‘A’ is accessing attributes from classes ‘B’, ‘C’ and ‘D’.
In this case, FDP of method ‘M’ is 3.