Re: Object Databases good or bad ?

Ulrich wrote:

> Can anyone please tell me where I can find out more on the strengths and
> weakenesses of an object oriented database. Is integrating a programming
> language with the persistence like in Gemstone/s/j really such a good
> thing ? Are object databases really the future ?

My epiphany came several years ago while reading up on object models ... mainly because, like I think you are hinting, I wanted to better understand how to appreciate them v. a relational model.

The cited example that gave me pause was: for a farmer, cow is the noun and milking is the verb, whilst for a dairy milk is the noun and "de-cow" is the verb.

Yes, exactly, right there are encapsulated the *two* reasons object modelling doesn't work:

• Object-oriented has too much perspective involved at the data level. For general modelling, we'd need to dig deeper to understand that *both* cow *and* milk are the nouns so that we can support *both* perspectives through a "subschema" mechanism.
• Object-oriented tries to include methods, the dynamics of the system. Data models need to be point-in-time snapshots, focussing purley on the data attributes associated with the problem, and the relationships between them at those points in time. The methods, again, belong as part of the "perspective" layer, the "subschema" again, above the full data model.

Bottom line is that most of the object-oriented stuff fails to properly consider the implications of persistence (which applies to a state as captured by a data snapshot), and over-simplifies the long-term management of the state transition processes.

I'll go and don my fire-retardent clothing now ... :-)

Barry J. Received on Mon Feb 12 2001 - 20:37:58 CST