Re: Mixing OO and DB

From: David BL <davidbl_at_iinet.net.au>
Date: Mon, 11 Feb 2008 08:10:53 -0800 (PST)
Message-ID: <1ce034c3-ce11-439e-9650-bb9b0d5a149b_at_i12g2000prf.googlegroups.com>


On Feb 11, 11:08 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
> On Feb 11, 12:44 pm, David BL <davi..._at_iinet.net.au> wrote:
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> > On Feb 11, 8:07 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
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> > > On Feb 11, 2:05 am, David BL <davi..._at_iinet.net.au> wrote:
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> > > > On Feb 11, 3:29 am, JOG <j..._at_cs.nott.ac.uk> wrote:
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> > > > > On Feb 10, 5:45 pm, "Dmitry A. Kazakov" <mail..._at_dmitry-kazakov.de>
> > > > > wrote:
> > > > > > [What is data, in your opinion?
>
> > > > > Data. Lots of datum - from latin, meaning statement of fact. Predicate
> > > > > and value in FOL. A value without description is of course just
> > > > > noise.
>
> > > > Latin datum is past participle of dare, "to give". What make you say
> > > > data is necessarily a set of propositions?
>
> > > The OED. "Facts, esp. numerical facts, collected together for
> > > reference or information." The etymology stems from 'dare', because
> > > facts are always communicated or "given". I understand of course that
> > > the term is thrown around wantonly and ambiguosly nowadays, but as
> > > data theorists, we shouldn't be party to that imo ;)
> > > > Are you suggesting a value
> > > > is meaningless without a proposition? Why can't a datum just be a
> > > > value?
>
> > > Because ta value has to be associated with something. Hofstadter gave
> > > a good example of this with the groove modulations on a vinyl record.
> > > To us they are (musical) data, to an alien not knowing their context,
> > > it is not. You need the context.
>
> > > > Wouldn't you say a recorded image is data?
>
> > > Of course, so long as I know it's an image. If its just ones and
> > > zero's stored in a computer, without anyway of telling they represent
> > > a picture, then it is simply noise.
>
> > Let's indeed assume we know how to interpret the 1's and 0's as an
> > image. So what have we got? Nothing but a *value*.
>
> No, you now have a value with applied context. That creates a fact.
> You now therefore have data. It's simple to show - consider "1000001".
> Thats currently a value, but its not data. Its only data when I store
> it, and state one of the following:
>
> "100001" is a text string
> "100001" is an integer (i.e. 65)
> "100001" is an ascii character (i.e. A)
> etc..

These "facts" are all tautologies that are true whether you record them or not. I dispute your premise that the purpose of the data in this case is to state a fact that is known a-priori to be true. If that is its purpose then it conveys precisely zero information.

> > We can display
> > it. We can comment on whether we like it - even if we haven't a clue
> > where it came from. But I don't see any sense in which the image
> > value gives us any statements of fact beyond the specification of a
> > value. A value simply "is".
>
> > I would suggest that a lot of the data in the world is characterised
> > more closely as "interesting values" than collections of
> > propositions.
>
> You cannot store these interesting values without implicitly stating
> some fact about them.

By definition, when a value is specified, its type is specified as well (except possibly if type inheritance is supported).

C. Date states the following in "Introduction to Database Systems", section 5.2, and subsection titled "Values and Variables are typed":

    "Every value has ... some type...Note that,     by definition, a given value always has     exactly one type, which never changes.     [footnote: except possibly if type
    inheritance is supported]"

When a particular value like the integer 73 is specified, there is no implicit fact being specified. The statement that the integer 73 exists in any absolute sense is entirely metaphysical and meaningless within computer science. Received on Mon Feb 11 2008 - 17:10:53 CET

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