Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

From: erk <>
Date: 8 Jun 2006 07:23:47 -0700
Message-ID: <>

Robert Martin wrote:
> Are you suggesting that RDBs cannot have duplicate rows, or even
> duplicate tables?

Right. Duplicate tuples in the same relation violate the relational model. The term "duplicate table" is slightly confusing, but if you mean 2 tables with exactly the same predicate (aka meaning), then I would call it a worse violation than duplicate rows, since in the absence of constraints, it introduces the possibility of update anomalies (inconsistencies).

If the relations have the same structure, but have different associated predicates, then it's not necessarily a violation.

> In any case, would you rather that your laptop prevented you from
> making copies of your files?

Apples and oranges, but yes, given a powerful file system (e.g. not strictly hierarchical), I wouldn't need a copy. Windows has shortcuts, *nix has symbolic links.  

  • Eric
Received on Thu Jun 08 2006 - 16:23:47 CEST

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