Re: what are keys and surrogates?

Jan Hidders wrote:

> On 19 jan, 02:48, David BL <davi..._at_iinet.net.au> wrote:
> 

Logical representations are representations to users. Physical representations are representations to the machine.

 From that, I conclude representations are not limited to representing to users.

I repeat: Why do you think representations are limited to representing to users?

>>>>>>>>I don't. I think possreps are. But I could be wrong about their
>>>>>>>>definition.
>>
>>>>>>>I strongly suspect you are.
>>
>>>>>>>>So what is exactly a possrep according to you? Are you
>>>>>>>>saying that the number of possreps of a certain value is by definition
>>>>>>>>the number of ways it can be represented as ... as what?
>>
>>>>>>>I don't understand the part starting with "as". I would punctuate the
>>>>>>>sentence there instead.
>>
>>>>>>I think you want to be more specific on what a representation exactly
>>>>>>is. That it should be something that can be presented by a computer to
>>>>>>a user on screen or a paper, for example.
>>
>>>>>A poor example.
>>
>>>>*shrug* Unless you are going to substantiate that, that is not really
>>>>a very interesting response.
>>
>>>I don't see any need to respond to straw men beyond observing that they
>>>are straw men. So, you want to assume that "possible representations"
>>>relates exclusively to human users to what end? To prove your axiom?
>>>Your axiom is false in the first place.
>>
>>>Assuming it to prove it is mental masturbation. If you want to engage in
>>>such activities, please do so in private.
>>
>>Jan simply asked Badour to clarify what is meant by a representation
>>and Badour responds with the straw man defence.

Jan simply constructed a straw man to burn, and Badour obligingly pointed out the deficit of his sophistry.

>>>>>A string, would be my first
>>
>>>>>>guess. Other representations like smoke signs, chalk marks, a series
>>>>>>of coughs, etc. are clearly not very relevant for the question in how
>>>>>>many ways you can map it to the physical layer.
>>
>>>>>I disagree.
>>
>>>>No kidding. :-)
>>
>>>>>>>>>How does representing to a user differ from representing to a machine?
>>
>>>>>>>>You don't get out much, do you? :-)
>>
>>>>>>>That kind of man-machine interface never even occured to me. One wonders
>>>>>>>what causes your mind to wander in that direction.
>>
>>>>>>I was only half kidding. A possrep is a notion at the logical level,
>>>>>>and therefore a matter of agreement between people. It is how a
>>>>>>certain set of persons agree to communicate a certain concept. For a
>>>>>>mapping to a physical level there is no such agreement necessary.
>>
>>>>>Indeed. However, every mapping to the physical level starts with a
>>>>>possible representation. Double or triple the number of possible
>>>>>representations, and one doubles or triples the number of possible
>>>>>physical representations.
>>
>>Note this well!

Indeed. One would do very well to contemplate the point made.

>>>>No, it doesn't. Increasing or decreasing the number of possible
>>>>representations does not influence the number of ways you can store
>>>>it.
>>
>>>You are talking nonsense. One cannot increase or decrease the possible
>>>representations for a data type. What's possible is always possible and
>>>what's not is not.
>>
>>On its face that contradicts Badour's earlier statement where he talks
>>about doubling or tripling the number of possible representations.
>>
>>Perhaps he would say his previous statement concerned comparisons of
>>*different* data types;

Of course, it does. I thought that would go without saying. Apparently, I was wrong.

however it seems remarkable to claim that
>>unrelated data types would always exhibit such a similar ratio of
>>number of logical to physical representations.
>>
>>For a given data type the possible logical representations are *user
>>defined*,

Hell no! The possible representations are all possible regardless of declaration to the dbms. What the possrep concept does is provide a way to declare some subset of them to the dmbs.

  and therefore one can make sense of Jan's remark of
>>increasing or decreasing the possible
>>representations. There is no mathematically defined concept of an
>>absolute set of all possible logical representations. Evidently such
>>a set would be infinite. It comes down to human judgement as to which
>>ones are deemed useful. For example, representing the dimensions of a
>>rectangle using the quarter-width and the fifth root of the radius of
>>the circle of equal area is technically a possible logical
>>representation, but hardly practical.
>>
>>>It might give you new ideas, but does note create options that you
>>
>>>>did not have already before. There simply is no direct relationship.
>>
>>Exactly.
>>
>>
>>>I have no idea where you get the idea that a data type with exactly two
>>>possible representations has exactly equal flexibility at the physical
>>>level as a data type with ten possible representations. The idea is
>>>absurd on its face.
>>
>>>I have no choice but to cite Date's _Principle of Incoherence_.
>>
>>"exactly equal flexibility" are strong words...
>>
>>I don't believe Jan stated nor implied that different data types have
>>the same number of physical representations.

Either he did exactly that, or he hallucinated some system whereby physical representation is not in any way connected to the values represented.

>>>>>>makes these notions fundamentally different. More to the point, you
>>>>>>could have six ways to represent the number 5, but let the DBMS store
>>>>>>it always in the same way.
>>
>>>>>But one would have to choose a possible representation. Choosing a
>>>>>representation that does not possibly represent the value seems pointless.
>>
>>>>It would do so by definition.
>>
>>>And the more possible representations, the more options one has at the
>>>physical level. I don't know why you have such difficulty with such a
>>>simple concept.
>>
>>Shouldn't Badour merely say there will be some positive statistical
>>correlation?

Don't should on me.

>>>>> Or you could have only way to represent it,
>>
>>>>>>but have six ways of storing it.
>>
>>>>>If one has six ways of storing it, presumably one has six ways of
>>>>>storing each of the possible representations. Thus, the number of
>>>>>physical representations grows linearly with the possible representations.
>>
>>Am I reading this right?

No, you are not.

Badour seems to assume that a given physical
>>representation coincides with (only) one of the logical
>>representations.

Hell no! Stick to what Badour actually says. If one has 6 physical ways of storing an arbitrary representation, presumably one has 6 physical ways of storing each possible representation. If I had meant to say the number of physical representations exactly equals the number of possreps that's exactly what I would have said, you fucking moron.

Instead, I said they grow linearly because that's what happens.

   Does he think there will actually be 36 distinct
>>physical representations?
>>
>>[snipped insults initiated by Badour]

> 
> That seems to me like a pretty accurate analysis of the discussion so
> far. 

Just because he kisses your ass doesn't make his analysis accurate. His analysis was fucking clueless and totally inaccurate.

So kudos for that. I actually don't have much to add to that, and

> since at least some of the audience seem to have understood my point,
> I'm just going to hang back and see if and how Bob responds.
> 
> -- Jan Hidders