Re: foundations of relational theory? - some references for the truly starving

"Marshall Spight" <mspight_at_dnai.com> wrote in message news:B6nmb.22188$e01.46207_at_attbi_s02...
> "Mike Preece" <michael_at_preece.net> wrote in message
news:1b0b566c.0310240556.3bf271e6_at_posting.google.com...
> > >
> > > BS. Or do you mean you don't write to log files ?
> >
> > No - we don't usually. It's not usually wanted or needed. We can if
> > you want. It's very easily done - centrally, with a trigger fired when
> > the file is updated if you'd like.
>
> So, what happens if you have a power failure or an OS or application
> crash when you've written the first page of a two-page update?
> Does Pick have transactions?

Does any primitive file processor? (It's a serious question. I would be interested to know which do.)

> > Ah - now there's something interesting! I often see people use "then"
> > when I think they mean "than". Is this an american thing or what?
>
> I suspect Costin is not a native speaker of English. While he
> is, in fact, jaw-droppingly educated as near as I can tell, his
> diction is idiomatic in a way that sounds distinctly non-native
> to me, an American.

Je pense que le singe ridicule est français.

> > Databases exist to record and retrieve data.
>
> I've always felt that this is what filesystems are for.
> Database management systems are for quite a number
> of more interesting and useful things, (in addition
> to being useful for data persistence.)
>
> In fact, I can imagine situations where I *wouldn't*
> need persistence but I would want a DBMS. If
> I was crunching up a bunch of numbers and was
> happy to restart upon a crash, say.

I expect this is what "in-memory" dbmses are for.

> > And 'normalisation'? You have to fit your data into a 2 dimensional
> > structure although you get the sneaking suspicion sometimes that it's
> > actually a lot more difficult to do so than it should be somehow?
>
> Well, it never seems that difficult to me, but I've been taught
> how to do it.
>
> BTW, normalization is the process of removing redundancy
> from a schema. A fully-normalized schema is said to have
> no redundancy, not be fully two dimensional.

A fully-normalized schema can have considerable redundancy. It just has no redundancy that one can remove with lossless decomposition using project.

> Actually, calling relations "two dimensional" is a common
> misconception. Relations are not two dimensional; they
> are n dimensional, where n is the number of attributes.
> You can print out points in an n-dimensional space on
> a piece of paper by listing the value in each of the n
> dimensions one after the other, one per line; that
> doesn't make the data two dimensional.
>
> Here's some different examples of colors from the
> three dimensional eight bit RGB color space:
>
> R G B
> ---------
> 255 0 0 // red
> 127 127 127 // gray
> 0 255 255 // cyan
> 0 255 0 // green
>
> Is this data three-dimensional or two dimensional?
> Answer: the data is three dimensional, but the
> presentation of the data is two dimensional
> if you view it on a monitor. If you view it
> on a punch tape, the presentation would
> be one-dimensional.)
>
>
> Marshall
>
>
Received on Sat Oct 25 2003 - 16:06:30 CEST