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Re: Data Constraints AND Application Constraints

From: Kenneth Downs <knode.wants.this_at_see.sigblock>
Date: Fri, 18 Mar 2005 23:18:32 -0500
Message-ID: <jqlsg2-mq8.ln1@pluto.downsfam.net>


-CELKO- wrote:

> I agree with you about checking data at each tier.
>
> But what I would really like is to have a "rules engine" that would
> help me generate SQL check constraints as well as 3GL if statements. I
> would also like to have my tool put the rules together in a decision
> table or something similar so I can validate and optimize them.

I'd love to discuss the shape of that rules engine with you, and the method of implementation.

For instance, it seems to me that Declarative Rules == Data Dictionary. Meaning a body of declarative statements is essentially a series of propositions about data. Or as we like to say, it is meta-data. So it seems the real question is, what is the structure of the meta-data tables? The answer to that question determines the capabilities of your engine.

Simple, right? Set up the tables and code away. But there is a fly in the ointment. Alas, one of the greater satisfactions I've had in life was working out my own approach to this, which I am now using to deliver systems to clients. Unfortunately, in order to have it generate the things you mention, you have to make judgement calls, you have to pick sides over and over again on many issues of dispute, and you have to do it at all levels. What this means is that absolutely everybody who has ever written a line of code can tell you what is "wrong" with your design. It's hard to talk about because every single aspect of it invites debate.

For instance, when you and the committee crafted SQL, you gave it features that are not relational. Why? It was a judgement call (I presume), a taking of a good idea forward into implementation and saying, "here is where theory meets reality and gives us a productive system". To get that rules engine you have to take more such steps.

-- 
Kenneth Downs
Secure Data Software, Inc.
(Ken)nneth@(Sec)ure(Dat)a(.com)
Received on Fri Mar 18 2005 - 22:18:32 CST

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