Re: Mixing OO and DB
Date: Wed, 13 Feb 2008 12:22:20 GMT
Message-ID: <0iBsj.7161$R84.2358_at_newssvr25.news.prodigy.net>
"David BL" <davidbl_at_iinet.net.au> wrote in message
news:8c33acce-694e-4edf-8758-7b296ea59557_at_s8g2000prg.googlegroups.com...
> On Feb 12, 10:49 am, "Brian Selzer" <br..._at_selzer-software.com> wrote:
>> "JOG" <j..._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.
> > Instance of a value? Context of a value? Possible value? Actual > value? I cannot make sense of that.
Perhaps I should clarify: A database is a proposition--a picture of the universe. There can be many possible pictures of the universe, but only one is supposed to be true. A value can appear in many possible pictures, so it follows that a value can appear in a possible picture that is supposed to be true or in a possible picture that is not supposed to be true, /or both/. If a value is a fact, how, then, can it be both true and not true? An instance of a value, a value in context--the association of a value with a picture of the universe--on the other hand, /can/ be a fact because that association can be with a possible picture that is supposed to be true or with a possible picture that is not supposed to be true, /but not both/.
A value that appears in any possible picture of the universe is a possible value. A value that appears in the possible picture of the universe that is supposed to be true is an actual value.
Thus a value is just a value without some context. Once a value is given context, such as being stored in a database, or written down, or whatever, then it can be considered information. Each atomic value that is in the database is a datum simply because it is /in/ the database.
[snip] Received on Wed Feb 13 2008 - 13:22:20 CET