Re: Why are [Database] Mathematicians Crippled ?

Jan

Let's see if we can pick up the pace a bit.

So I have established, under Roman Dutch Law, in civilised countries that are not held hostage by gypsies, tramps, and thieves, the "professor" is committing three frauds, worthy of a medium prison sentence, and the authors are committing one great fraud, and the sentence is much greater, execution.

> On Tuesday, 3 February 2015 02:09:05 UTC+11, Derek Asirvadem wrote:
>
> Now the unchanging law is, since you are not aware of it, since 1970, Codd's definition of Third Normal Form. From memory (ie. I am happy to be corrected, but I expect any errors to be minor, unworthy of argument):
> ____ "Every non-key attribute is Functionally Dependent on the Key, the whole Key, and nothing but the Key"

In case you theoreticians are not aware, it follows from the above, for us undamaged humans, that "Key" identified, is a key issue. Without the Key, there is nothing for the attributes to be, or not be, Functionally Dependent upon. Therefore it is impossible to contemplate a Functional Dependency, unless and until one is choosing a Key. The Key does not have to be final, just an attribute set that is honestly being considered as a Key.

1. Post-choice of a Key, the FDs are used purely as a verification method. Very fast, very clera.
2. During the choosing of a Key, FDs are used deterministic method. A bit more work, but very clear.
3. Prior to choosing a Key, FDs are pure conjecture, because there is nothing for the attributes to be Functionally Dependent upon. So even if they idea was contemplated, it really should be named something else, not FDs. To the extent that the theoreticians use the term for [3], it is fraud, confusion at best.

[3] has no clarity at all, it is confusing to most people to whom it is given. It is slow, until such time as a meaningful goal is given.

So in the physical universe of practitioners, only [1] and [2] exist. [3] is unknown, and if considered, quite laughable, pointless, needless.

Then there are a few practitioners, such as yours truly, who know a tiny bit about what theoreticians do in their MMM workshops. They have figured out, that by trying all the permutations of the possible "FDs", on all the attribute sets and subsets, such that when certain magical mystical combinations occur, woohoo, they have determined a "key".

Marvellous.

Wonderful.

Give the magician a gold star and a pointy hat. One more elephant hair has been determined, but they are still clueless about the elephant.

Codd gave us the definition of a Key: "it is made up from the data, a subset of the attributes that uniquely identify the row (tuple)"

Can any of you give me an example of where any company on the planet uses 1's and 2's or x's and y's as attribute values ?

Right.

So the fact is, that the key-determination-via-non-functional-dependency method is good for nothing in the physical universe. But there is a learning value.

If the examples used real data values, instead of 1's and 2's, the kids might learn something. Otherwise it is a Japanese puzzle for 3-year-olds, using 1's and 2's instead of 1-to-9's.

The "professor" is trying to teach that[3]. Not [1], not [2], but [3]. But the title is [1]. If he was teaching [3] properly, then he would introduce and explain what the concept is, then he would teach it. He doesn't. He launches into the most idiotic, useless, meaningless use of FDs, without explaining a thing, without teaching [1], then[2], then: oh, btw, here is a neat trick if you ever are in the position where you cannot determine the key, here is [3].

So the evidenced facts are (check the video), he is teaching [3] with no introduction or explanation, under the title of [1].

Hence my initial comments re the hairs on his head, the fish in the sea.

Hence my initial comments: he is clueless *about* the subject; he is clueless about *how to teach* the subject; but he is teaching it anyway, under a title that is well-established. Fraud count number four.

And again, if alien magicians wrote books, that instructed him to teach FDs like this [3][1][2], backwars and upside-down, severe fraud count two against them. Fifty lashes before the hanging, and hanging upside-down.

I hope I have bridged the chasm, at least in this one small subject. The level of understanding, the distance between the theoreticians in this field, and ythis field, is like the Grand Canyon.

Cheers
Derek Received on Mon Feb 02 2015 - 17:51:00 CET