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From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.object
Subject: Re: Updates on class taxonomy
Message-ID: <1991Jan15.152723.3862@tukki.jyu.fi>
Date: 15 Jan 91 15:27:23 GMT
References: <91Jan14.165013est.7093@neat.cs.toronto.edu>
Reply-To: sakkinen@jytko.jyu.fi (Markku Sakkinen)
Organization: University of Jyvaskyla, Finland
Lines: 32

In article <91Jan14.165013est.7093@neat.cs.toronto.edu> vinay@cs.toronto.edu ("Vinay K. Chaudhri") writes:
>
>Once an object taxonomy has been defined, how often does one need to
         ^^^^^^^^^^^^^^^ (1)
>change that information ?  Is it reasonable to say that this 
>information is equivalent to the schema information in 
                ^^^^^^^^^^^^^^^^^^^^^^^^ (2)
>relational datbases and thus will be hardly updated ?  
                              ^^^^^^^^^^^^^^^^^^^^^ (3)

By (1), do you mean only the inheritance graph between classes
or the complete class definitions?  If the latter, then you can
well say (2), but that does not necessarily imply (3)!

>If the updates are required should they be on-line or off-line ?  
>How frequent are the updates ?  What are the good examples of such updates ?
>Should they be done one at a time or should be permmitted concurrently ?

Updating the definitions of classes while they have instances
continues to be a hard and important research problem for OO databases.
One not too difficult new paper by Staudt Lerner and Habermann
is in the OOPSLA/ECOOP'90 proceedings: "Beyond Schema Evolution
to Database Evolution".  You can expect to find something in this area
in the proceedings of virtually any recent database-related conference.

Markku Sakkinen
Department of Computer Science and Information Systems
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland
          SAKKINEN@FINJYU.bitnet (alternative network address)