From: Erwin <>
Date: Sun, 5 Sep 2010 07:22:22 -0700 (PDT)
Message-ID: <>

On 5 sep, 14:44, Brian <> wrote:
> Under the closed world
> interpretation, on the other hand, it /is/ automatically assumed that
> the corresponding proposition is false.

So, you agree that under CWA, "tuple absent" implies "proposition false".

> In other words, if you don't
> know, then it ain't so.

What is not known is not worth being considered, except for the effort of making it known. That effort is of no relevance in DBMS technology.

> Under both the open- and closed-world interpretations, only
> tuples that represent what is known to be true appear in the database;

So you agree that under CWA, "tuple present" implies "proposition true", or NOT("tuple absent") implies NOT("proposition false").

Combined with what you previously agreed upon, this means that under CWA, there is a bi-implication, aka equivalence, between "tuple absent/ present" and "proposition false/true".

Meaning that the CWA allows me to determine whether some tuple ought to appear in the database by checking in the real world whether the corresponding proposition is true or false.

You claimed at one point that the meaning of a tuple is somehow "yet a bit more than just the corresponding proposition". Making the decision process of whether or not a given tuple ought to appear in the database one that is more complex than it needs to be. Received on Sun Sep 05 2010 - 16:22:22 CEST

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