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From: kelly@ug.cs.dal.ca (Michael Kelly)
Newsgroups: comp.lang.c++
Subject: Retrieving objects?
Message-ID: <1991Apr12.154914.9817@cs.dal.ca>
Date: 12 Apr 91 15:49:14 GMT
Sender: news@cs.dal.ca (USENET News)
Distribution: ca
Organization: Math, Stats & CS, Dalhousie University, Halifax, NS, Canada
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This is really a two part question:

1) if PERSON is a class and EMPLOYEE is a subclass of PERSON and 
   TOM is an instance of EMPLOYEE then TOM is a PERSON right?

2) ok, now assuming TOM is a PERSON, but is really an instance of 
   EMPLOYEE, how is TOM stored so that when I ask for all instances
   of PERSON I will get TOM?
   ie. is TOM's object ID somehow associated with the class PERSON?
   I am looking for an answer in terms of persistent object storage.
   ie. how is TOM represented if I save my system to disk such that
   I can retrieve the object TOM and know it is a PERSON and an EMPLOYEE?

Please e-mail any help,
kelly@ug.cs.dal.ca

PS.  Please excuse any obvious demonstrations of ignorance.