Defining referential integrity with alternative tables

[tomas bar]

Hi,

Is it possible to define a relationsip between a table and a number of alternative tables?
For instance if you have a table PEOPLE and one of the fields is VEHICLE_OWNED.The value of this field can be the primary key of either table CARS or table BICYCLES or table BOATS.
Is this design conceptually sound and how can this kind of referential integrity be defined? do you need triggers?

Thanks a lot.