Object IDs vs relational keys?

[Amir Ansari]

>From my background reading on object databases:

"A relational database represents data relationships by having matching primary key-foreign key data. There are no data structures within the database that form links between the tables; the relationships are used as needed by joining tables. In direct contrast, a pure object-oriented database 'hard codes' its relationships by including object identifiers within an object to indicate other objects to which it is related."  (Object-Oriented Database Design, Jan L Harrington, Chapter 3)

I've pored over the Magma documentation and mailing list, but couldn't find any explicit discussion of object identifiers in this context. I understand that Chris is loth to use OIDs (http://lists.squeakfoundation.org/pipermail/magma/2005-August/000027.html), so what's the alternative? What is the Magma analog of 'joining' tables using primary/foreign keys?

Amir