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Re: All hail Neo!

From: Frank Hamersley <terabitemightbe_at_bigpond.com>
Date: Wed, 26 Apr 2006 06:06:49 GMT
Message-ID: <Z5E3g.16142$vy1.3861@news-server.bigpond.net.au>


Bob Badour wrote:
> Frank Hamersley wrote:

>> Bob Badour wrote:
>>> Frank Hamersley wrote:
>>>> Bob Badour wrote:
>>>>> Frank Hamersley wrote:
>>>>>> Bob Badour wrote:
>>>>>>> Frank Hamersley wrote:
>>>>>>>> Bob Badour wrote:

[..] time for a haircut!

>> OK - I presume the dichotomy is practice (SQL) vs theory (RM) in that
>> with the former tables can exist with repeated rows but in the latter it
>> presumes in a relation all tuples are distinct?

>
> Since SQL and RM are both theory and practical, your sentence is nonsense.

Preempting some of your various replies below you seem to be getting fatigued of this topic. Regardless, for me the RM is the theory and SQL is the practice. Sure the latter "contains" some or all the former but using this distinction adequately provides terms or reference for me as "where we are" against "where we want to be". I don't think I can help you much more than that.

[..]
> Missing information is messy and we have no theory at all for addressing
> it. Adding it to the RM in no way reduces the elegance, symmetry or
> compellingness of the RM.

Rubbish - IMO the whole is less for the adding the messy bit without resolving it to meet the ES+C criteria. Sure the other parts are just as ES+C as they were before when taken in isolation. This is akin to the mess that existed in the prediction of planetary orbits prior to Newtons apple.

> Either one can use the E,S&C to tackle the
> difficult problem, or one can pretend the problem doesn't exist.

This sounds overtly minimalist on your part. If I read it correctly on the one hand you state there is no theory to support missing info and then you propose to solve the issue solely with the theory at hand whilst dismissing all other possibilities - to toss in a barb that seem as ostrich like as it gets.

> Null pretends the problem exists.

There is no need for pretense is there?

> It reduces the expressiveness of the
> language and hides people's errors from them. Can you imagine a compiler
> that refused to reject any program or issue any warning?

Nup - unless the optimizer deduced the erroneous code was unreachable! That of course would be pointlessness^2.

In the same vein can you imagine a compiler that checked for speeling (sic) mistakes in manifest string constants?

[..]

>>> Whether nulls exist in the RM today is a topic of some controversy.
>>
>> Sure is - in biological terms noting that the bastard child SQL 
>> inherits only half its genome from the known parent (RM) then the 
>> question is - is it a meiotic mutation or a pre-existing recessive 
>> allele now homozygous and perhaps deleterious?

>
> Nonsensical handwaving.

Is this code for I don't understand or simply can't be bothered? If so I will happily limit my discourse to a dry form however I had picked you as a well read energetic type.

[..]

>> By logical identity I take it you mean the distinctness of each tuple?

>
> The identity of every explicit value in every relation. Since tuples are
> values, logical identity includes those.

OK.

[..]

>> Yep  - although there probably no debate to be had once the various 
>> and varying starting points are determined.

>
> More nonsensical handwaving. You have succeeded in one thing with your
> evasiveness: you have demonstrated your lack of intellectual honesty and
> integrity.

More fatigue? Its pretty simple really - if I start with your assumptions I agree your conclusions. If I vary them we end up apart. Should I vary them? That is the point of interest for me at least - if that is tiresome for you - ce la vie.

[..]

>> OK. Obviously useful for the theorist to explore stuff (apols to Alexi).

>
> Obviously useful for the practitioner to explore as well. If the
> practitioner never considers where the pitfalls lie, he will only
> discover them from the bottom of the pit.

Sure - and these pits are often filled with tar! What I was alluding to is a practitioner accepting the theory can avoid exploring the pits by sticking to the provided map. Of course it is a worthy goal for all practitioners to understand as well as apply best practice.

[..]

>> So {1} and {1} are not distinct when conceptually imagined in an OO 
>> instance frame of mind?

>
> An OO instance is a variable. Thus the values of the two variables are
> indistinct even if the variables themselves are distinct and
> distinguishable by physical location.

No drama here.

>> Thus it would take something like {1,2} and
>> {1,3} at which point the sets are distinct?  In this case are the 1's 
>> distinct?

>
> No, they are not. The value 1 is the value 1. They are equal. You have
> given no other way to distinguish the values. In fact, in set theory:
>
> {1} = {1,1} = {1,1,1}

OK.

>>> However, a single attribute within a single tuple within a single 
>>> relation variable has a unique logical location.
>>
>> True.
>>
>>> How then can null equate to two locations?
>>
>> I'm guessing a bit here about your question - I take it to mean 
>> {1,null} and {1,null} should not be seen as distinct but nVL insists 
>> they are?

>
> No, I was shredding your earlier try at an answer when you replied with
> "{}{}=null".
>
>>> What then does it mean when the null appears in a derived value which 
>>> has no location at all?
>>
>> But the RM proscribes every value (derived or not) has a location does 
>> it not - that is putting aside the stuff about nameless or duplicated 
>> attributes etc?

>
> In the RM, logical identity locates a value within a variable. One can
> change part of a variable for instance and the value at one or more
> physical location(s) will change. The fact that values outside of
> variables have no location further shreds your attempt at a reply with
> "{}{}=null".

Hmmm - I thought we had got past this windmill - we have now?

[..]

>> No, I don't think it does. As you say it is not {} and {null} does not 
>> equal {null} - this is as I said before a paradoxical state of affairs 
>> and clearly does not marry well with the formal approach to analysis.

>
> And since all of programming is about formalism, I suggest null has no
> effective role to play in any aspect of programming.

Very sloppy words! I would say intellectual honesty arises when you are prepared to say something like "since all of programming *theory* is about formalism, I suggest null has no effective role to play ..." Of course I would be interested to see you ante up and describe a fundamental and complete solution rather than simply taking your bat and ball home.

[..]

>>> Are you familiar with Date's various _Writings..._ books? He and 
>>> Darwen and others have demonstrated that null causes great damage.
>>
>> I don't need them to postulate it as I've seen it first hand.  My 
>> opinion of Date mainly and Darwen to a much lesser extent (more by 
>> association than real research) is that whilst they have taken a pot 
>> shot at a low flying albatross, they haven't come up with anything 
>> even close to better.

>
> I disagree. They have correctly identified that missing information as
> of yet has no theory to address it.

That is a trivial conclusion! Where's the beef? You don't need to be a luminary to get this far - do you?

> While I disagree with some of their
> ad hoc attempts to address it differently than null, I suggest the RM --
> without any special feature for missing information -- already handles
> it as well as we can until someone establishes a valid theory addressing
> missing information.
>
> Null takes a bad situation and makes it worse. It does harm. Removing it
> improves our lot.

I'm all eyes! I'm happy to consign null to oblivion if you give me a _credible_ solution which means it must meet ES+C to accommodate my limited analytical abilities.

>> Given the lesser evil option I expect to rely on skilled practitioners 
>> to mitigate the risk of that damage arising.  Sadly they don't grow on 
>> trees!

>
> All the more reason to make simple queries easier to express correctly
> so casual users do not have to waste the time of skilled practitioners
> for very common, mundane queries.

I can relate to that - but I for one don't see your mundane queries as in the problem domain. Viable practitioners can design RM compliant systems using SQL if required. The real issue is solving the difficult queries - something which D+D skate glibly over as I pointed out.

>>> Nulls attempt to address missing information but do so with no basis 
>>> in theory. I suggest that the null elixir only offers the illusion of 
>>> power:
>>> http://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/EWD898.html
>>
>> I understand your view. For the record mine is that null is no elixir 
>> - more like Cod Liver Oil and there ain't no illusions when swallowing 
>> that stuff.

>
> If one takes the average age of a group of people where some of the ages
> are unknown, then the average is unknown. With a relational dbms, I can
> model the ages so that it returns the correct result, unknown.

I can cope with that - I would have no problem being forced to write

"select avg(age) from table where age is not null"

to get the crappy statistic that it is if the user demanded it. But I thought you wanted to eradicate the nulls period?

> When the user gets the result, the user has to ponder what that means
> and how to proceed. If the user discovers that back in the old days
> nobody bothered to record birthdates, the meaning is different than if
> the ages are unknown because some of the people are fetuses as of yet
> unborn.

You are taking on too much methinks - if a mug user wants to buy birthday presents for fetii why should the RM be saddled with saving him from his own stupidity. Better IMO to focus on those who want to be saved.

> Null is less expressible than the RM because it obviates the possibility
> of returning the correct result. The result it returns is incorrect and
> in the cases mentioned above is not even approximately correct, but the
> user has no alert to the problem.

Unskilled users yes - as for me I am prepared to take my chances until the GUT (Grand Unified Theory) arrives at which point I will happily adopt it.

> If that is not an illusion of power, I don't know what is. As a solution
> for the problem of missing information, null is an elixir. Since your
> earlier evasiveness has revealed your lack of intellectual honesty, I
> will dismiss your denials as groundless.

Ah well we all have crosses to bear - suffice to say there are no illusions on my part.

[..]

>> That is how I would characterise "D".  On the theory side I am in a 
>> prolonged contemplation on the missing dimension in SQL (as compared 
>> to the RM) which is the temporal capability.  I have made what I 
>> consider to be some progress but it is premature to discuss publicly 
>> lest I end up wearing lots of egg, suffice to say the null thang has a 
>> parallel in temporal matters.  BTW I don't rate Date & Darwens 
>> offering on this either, nor FWIW much of the Snodgrass et al stuff 
>> that preceded them.

>
> Yes, well, get back to us when you have something substantive to offer
> that won't leave egg on your face.

No problem. In the meantime I am happy for you to advance something more than a simple change to the behaviour of avg().

Cheers, Frank. Received on Wed Apr 26 2006 - 01:06:49 CDT

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