Re: Example of expression bias?

From: Tony D <>
Date: 20 Jun 2006 08:55:05 -0700
Message-ID: <>

Cimode wrote:
> Data types are not orthogonal to relations (in RM), they are integral
> part of RM definition.

Then we've just come to a shuddering halt in this discussion, because this is an unbridgeable gap. Relations are *very much* orthogonal to data types; the definitions of relation, tuple, attribute and the relational operators have only one thing to say about the data types to which attributes may belong - that a boolean equivalence function between two values of that type is defined. That's *it*. Nothing else, and nothing more.

If we can't agree on that, then yes, this discussion is completely null and void.

Since we're shuddering to a halt, I won't go through the whole post blow by blow.

> I have provided you with an analogy about the bus. Did you understand
> it? Do you still consider a variable as varying?

Taking a commonly used denotational semantics view of it, for a variable name the denotable value is a location, and a store is a function, mapping from a location to a value. The location won't change, but the value that location maps to will. Does that answer your question ? I was quite specific to say that in my post I was referring to C/Pascal/3GL style variables, rather than the mathematical/FP sense of variables.

[ snippage ]

> user defined types are a part of RM, they are defined as types of
> arbitrary complexity.

Care to vague that up for me a bit more ? It's not much of a definition; it's not much of a definition because data types are nothing to do with RM.

> From what I observe interacting with you and the level of confusion
> that seems induced by FP, I believe that it is a waste of time. Which
> I express...

Fair enough, you think I'm confused; in that case you owe it to yourself to consult better sources than me. You could *start* at wikipedia, which has some useful links on to other sites; or you could go to It's really up to you. And yes, it's your loss if you don't.

> What data management problems are you refering to? Be more specific...

Not every problem is a data management problem. For example, data type definition, about which the RM has nothing to say. As I said in the first paragraph, if we're not going to agree on that, then yes, future discussion will, as ever, generate plenty of heat and little light.

[ snippage ]

> A computer is a set of mechanized components regulated by electronic.

At the physical level, yes. At the physical level, they are also generally uninteresting lumps of plastic and metal. At the conceptual level of computable functions, electronics, electricity, plastic and metal are utterly irrelevant. Hence a comment I made before: all the really interesting results in computing science can be derived with a pen and piece of paper.

> The only way you can make inferences about data is by defining a
> logical computing model then derive an implementation physical model
> from that logical model.

Actually, you only really need what you call the logical computing model.

[ snippage ]

> I can not agree with confusion and vagueness. I have provided you with
> several definitions, analogies and proofs to proove your definition of
> variable was wrong. You have produced an exhortation to find out about
> FP

Where was your "proof", never mind several ? It can't have been the bus analogy, surely. And even then, we argued to agree.

> No it is a fact. SQL has been clearly identified by many RM people as
> having a very strong limiting effect on RM understand..Some people
> dumped it for more than 20 years ago because of that.

"No it is a fact." What is a fact, in either of the two sentences to which you responded ? SQL can only limit your understanding of RM if you allow it to. Once the differences have been pointed out, accepted and understood, it's pretty difficult to confuse them thereafter. (Whether you either discover the differences or have them pointed out to you is another matter entirely.)

> It was irrelevant when you give relevance to the premice behind the
> theory. I don't. I have been asking questions that have not been
> answered therefore I have to assume I was right.

I'm not clear on what your first sentence means. Which premise to which theory ?

I think you would assume you were right no matter what answer was given to you. Received on Tue Jun 20 2006 - 17:55:05 CEST

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