Re: Some Hype on "new" databases - where's the theory in this group?

On Sun, 08 May 2005 17:40:43 GMT, paul c <toledobythesea_at_oohay.ac> wrote:

>Alfredo Novoa wrote:
>
>> ...
>>> i've never seen any discussion of such basics in this
>>>'theory' group. how come? isn't this the kind of thing that should be
>>>discussed here?
>>
>>
>> This is. I am curious about your simple examples.
>
>thanks for comments. now that i've opened my big mouth, i guess i'm
>obligated to reply. i've forgotten exactly what they all were but one
>of them goes something like this. (i was interested in comparing <OR>
>and <AND>, not that an engine would depend on both, but so that it could
>use one of them plus <NOT> to check the other one, in other words to be
>able to check some of its own logic):
>
>
>TTM page 56 - manual check of meaning of <OR>
>
>Check R1{A,B} <OR> R2{B,C}
>where the domain of A is (1,2,3) such that 1=1, 2=2, 1!=3 and so forth
>and the domain of B is (1,2,3,4) et cetera
>and the domain of C is (1,2,3) et cetera
>and R1 = {{1,1},{2,2}}
>and R2 = {{1,2},{3,2}}
>
>then
>{{1,1},{2,2}} <OR> {{1,2},{3,2}}
>=
>{{1,1,1},{1,1,2},{1,1,3},{2,1,2},{3,1,2},{2,2,1},{2,2,2},{2,2,3},{1,3,2},{2,3,2},{3,3,2}}
>
>at least, that's how i worked it out using de Morgan's law.

I have got the same result.         

>2) when i say 'core' i'm excluding user interfaces. i mean, precisely,
>D&D's "ALGEBRA" although perhaps not all of it! (regarding interfaces,
>and IF i ever got around to making a "modern" one, at first, i thought
>of adapting openoffice but the idea of excising Java and XML from it
>distresses me. perhaps i would use Mozilla (not its so-called db
>support) and hold my nose regarding the XUL stuff which i admit is
>well-intentioned.)

IMO It would be a lot easier to create a simple user interface with Visual Studio or Eclipse.

>4) in my ignorance, i'm not bothered, at least not yet, by the
>"computational difficulties" of supporting <NOT>. given that we are
>talking computers here, then domains are finite in practice if not on
>paper.

But many of them are so big that they are infinite in practice.

>5) what really got me started along these lines, if i can use the word
>"started" to describe something that's just an occasional reverie, was
>trying to understand how far-reaching Codd's original operators were. i
>remember seeing that (with appropriate syntax and the help of immutable
>place-holders), the conventional verbs, INSERT and DELETE are
>expressible (i like to say inherent) with various combinations of <AND>,
><OR> and <NOT>, as are foreign keys and candidate keys (although it was
>some years before my limited brain realized the latter). this may seem
>trivial to some but it was greatly encouraging to me as was Hugh
>Darwen's kind replies to some confused questions i put to him. further,
>i think TCLOSE might be avoidable but i haven't quite put my finger on
>exactly how, though i have in mind an approach i once saw which would
>involve using intensions.

See page 163

>i would hope that in the 'core' there would be no conventional
>procedural programs as such, given the number support that i mentioned,
>and i would implement conventional locking, ala Gray, as well as a
>presentation mechanism, at an unconventional level, in a layer above the
>core engine which might add verbs for convenience but would depend
>entirely on relations implemented in the 'core'.

IMO it would be better to ignore concurrency issues until you have a working single user system.

>(aside - one motive here was partly avoiding bloat, relying on as few
>concepts as possible and having an engine that's easier to validate as
>well as to maintain.

It is very feasible IMO. But it would be something rather similar to Rel. http://dbappbuilder.sourceforge.net/Rel.html

I am working in something similar but built from scratch.

Regards Received on Mon May 09 2005 - 03:30:19 CEST