Re: Mixing OO and DB

From: Brian Selzer <brian_at_selzer-software.com>
Date: Tue, 12 Feb 2008 01:49:58 GMT
Message-ID: <aX6sj.8094$0o7.3296_at_newssvr13.news.prodigy.net>


"JOG" <jog_at_cs.nott.ac.uk> wrote in message news:27321846-87df-4f21-a7bd-382d8b7d6605_at_m34g2000hsf.googlegroups.com...

> On Feb 12, 1:01 am, JOG <j..._at_cs.nott.ac.uk> wrote:

>> On Feb 11, 4:10 pm, David BL <davi..._at_iinet.net.au> wrote:
>>
>>
>>
>> > 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:
>>
>> > > > On Feb 11, 8:07 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
>>
>> > > > > On Feb 11, 2:05 am, David BL <davi..._at_iinet.net.au> wrote:
>>
>> > > > > > On Feb 11, 3:29 am, JOG <j..._at_cs.nott.ac.uk> wrote:
>>
>> > > > > > > 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'm not seeing whats so controversial or difficult about the fact that
>> "10001" is just a meaningless binary value until you give it a
>> context. It seems somewhat obvious to me.
>>
>> > 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.
>>
>> A Datum is a given fact. That's what the word means formally. I have
>> said nothing more, and I have no idea what you are on about talking
>> about "the purpose of data".
>>
>>
>>
>> > 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.
>>
>> So you just wriite "73" down and are telling me its a datum? I'm
>> pretty sure that's what we call a "value", not data. I'm wondering if
>> you are misconstruing my point - "73" is only data when you apply some
>> context to it, like saying this its someones room number, or today's
>> average temperature, or the amount of red in a certain pixel of an
>> image (and yes, those are then facts).
>
> Let me clarify the distinction I'm making David:
> "RED" is a value.
> "The first pixel in the image is RED" is a datum.
>
> That can't be that contentious...can it?

Isn't a datum an atomic value? I think I remember reading somewhere, "Each and every datum (atomic value)...."

I think the distinction you want to make is whether or not some individual that is represented by the value 73 actually exists. For that there needs to be a context. If the value 73 from the domain of integers is named in a tuple in a relation in a database, then clearly that particular instance of the value 73 has a context and thus maps to an actual individual in the picture of the universe of discourse that is the database. Clearly the act of storing the value 73 gives it context. Without context, 73 is a possible value, not an actual value. Received on Tue Feb 12 2008 - 02:49:58 CET

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