one-to-many relationship - trick - several objects types to same object type

once again, i'm working on my object history abstract class. i have it
saving data properly but now i'd like to be able to access that data.
the historySet object contains the parents entity name and the primary
key. is there any way to form a link on those two kinds of data? I can
think of a number of compromises, such as linking only on the primary
key and then filtering on the entity type or simply creating an object
function that return the desired results.

any suggestions?

many thanks,
matt