Re: Two-valued logic

From: Dawn M. Wolthuis <>
Date: Tue, 30 Dec 2003 14:02:21 -0600
Message-ID: <bsslkh$2la$>

"Marshall Spight" <> wrote in message news:_sKHb.502995$275.1414945_at_attbi_s53... <snip>
> "In Defense of Nulls"
> For myself, I dislike 3VL, since I think it adds tremendous complexity
> but little expressiveness. The expressiveness it does add would be
> better dealt with in the type system, and not in the logic system.
Good article on nulls. I agree with him in defending nulls. However, I agree with you that there is not good enough reason to complicate things with 3VL. So, using Boolean logic with null treated as the null set seems like a very good approach. It makes it easiest for the average end-user to understand and query the data.

Since the old, but useful model I'm working with right now (Nelson-Pick) was developed in order to make it easy for the military in Viet Nam to query and understand their data without any DBA's or IT professionals in their midst, it is very pragmatic this way. This model seems to have good solutions to questions such as whether or not to use multivalued logic without having considered all options by thinking in terms of what would be most useful to their customers..

With Nelson-Pick, I'm backing into a model based on the highly usable implementations, whereas with RDBMS's, the database implementations are basedon the relational model. What I'm finding is that there are likely to be flaws (mismatches) in the model for Nelson-Pick just as there are mismatches in the implementations of the relational model. However, just as the relational model "works" well on paper, the Nelson-Pick implementations work well in practice.

My goal is still to get a good handle on why the theory I've read (relational database theory) and the experiences I've had (with many types of databases) are not in step. The Nelson-Pick model has yielded the more productive software development teams I've worked with, with the RDBMS's yielding the poorest productivity (seemingly worse than IMS and other older models). This is simply my experience, but I have anecdotal evidence that many others have seen the same disparity.

Both the hierarchical and Nelson-Pick databases pre-date the relational model. I'm certain we have gained something with RDBMS's, but it is really obvious to me that we have lost something as well -- developer productivity, ease of software maintenance = what are currently termed "agility".


--dawn Received on Tue Dec 30 2003 - 21:02:21 CET

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