Re: Mixing OO and DB

From: David BL <davidbl_at_iinet.net.au>
Date: Wed, 13 Feb 2008 19:52:38 -0800 (PST)
Message-ID: <9a04b6fc-f4e0-4d1e-8af5-02451db242eb_at_m34g2000hsf.googlegroups.com>


On Feb 13, 9:56 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
> On Feb 13, 2:06 am, David BL <davi..._at_iinet.net.au> wrote:
>
>
>
>
>
> > On Feb 12, 9:53 pm, JOG <j..._at_cs.nott.ac.uk> wrote:
> > [snip]
> > > Consider /unallocated/ RAM in your PC. Look at 5 contiguous bits at
> > > random. Are you telling me that the binary number you are looking at
> > > is "data"? I'd accept that it is a value (albeit a meaningless one)
> > > but "data"? You really think that?
>
> > No I don't.
>
> > When data is recorded on some medium there is a lot of implicit
> > *knowledge* about how it has been encoded. This knowledge has to
> > account for all sorts of details, such as what designates a 1 versus a
> > 0. How many bits in a word? What order do they appear in? Is there
> > an address bus? How is the address bus organised? The binary
> > encoding is only a tiny part of it. Obviously we both agree that all
> > that knowledge is implicit in correctly decoding the data.
>
> Yes I broadly agree apart from on one key matter (there's a suprise
> eh) - "knowledge is implict". I contend the exact opposite, and this
> is my whole point really. The knowledge required must be explicit.
> That's what makes otherwise random noise, or values, data. In the
> case of a scientist log book for example what the data means is
> explicit in a title at the top of the page or in the scientist's
> head.

You can't make the knowledge explicit because you can't formalise it.

> Another example:
> "todays lottery numbers: 23, 34, 17"
> "experimental reults: 23, 34, 17"
>
> Same values, different data. If you agree with this statement then
> values != data surely?

You seem to have forgotten that I said data was associated with the appearance (ie encoding) of values. Encodings have a context, and values do not. We don't disagree on whether data is associated with encodings. Rather we disagree on what is being encoded. I say data = encoded values. (I think) you say data = encoded facts.

> > Our point of contention is rather that I suggest that most generally
> > the data is nothing other than encoded values, and doesn't necessarily
> > convey any facts. I'm assuming that the knowledge implicit in the
> > encoding of the data is by definition not part of the data itself,
> > whereas I think you are suggesting it is part of the data.
>
> Yes I think that's an excellent breakdown. Its all just down to where
> we draw the lines I guess...
> Brian: Data is encoded values. I need to know externally what they
> represent.
> Jim: Data is encoded values plus an denotation of what they represent.

Did you mean to say Brian?

Do you agree you cannot formalise what the values represent?

> > I would prefer to say that the knowledge of the encoding (the
> > "protocol") exists independently of the recorded data (or even the
> > particular instance of the media it is recorded on). For example I
> > don't want to create a new file format for every file.
>
> > > > > > 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".
>
> > > > Let me use an example: I give you a disk with some data, tell you a-
> > > > priori that it records a string, describe the format and you are able
> > > > to determine that the recorded value is a poem
>
> > > > "Is it binary or is it data?
> > > > Is it info or knowledge,
> > > > or is it wisdom -
> > > > the whole enchilada?"
>
> > > Thats a value imo, and its only data if we say "The file myPoem.txt
> > > contains 'Is it binary or is it...'".
>
> > I don't know what that means or what distinction you are making. I'm
> > very suspicious of introducing a proposition that is referring by name
> > to the file. Names don't have absolute meaning. What is the context
> > for this proposition?
>
> > > I do realise that the
> > > definitions I am suggesting as formal are at odds to the handy wavy,
> > > nebulous way we throw around terms such as 'data', 'data model', etc.
>
> > > As proof (!) consider your above example if you placed the poem
> > > written on paper in front of me. Are you telling me that is data?
> > > Course not, its just a poem written down - a value. So then what is
> > > the difference between this and your example on a disk? That its
> > > encoded in binary?
>
> > Since this is a computer science discussion group I'm happy to narrow
> > the definition of data to encodings of values that are intended for
> > both reading and writing by a computer.
>
> > > > Note that no additional context has been provided. I would say the
> > > > purpose of the data was to convey a value, but not to convey a fact.
>
> > > > > > 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.
>
> > > > C.Date distinguishes between a value (that by definition doesn't exist
> > > > in time and space), versus the *appearance* of a value which appears
> > > > in time and space and is encoded in a particular way.
>
> > > Is this what your view of the terms is based upon?
>
> > These definitions seems reasonable to me.
>
> This seem overly philosophical to me. Surely we don't need metaphysics
> to know that if someone hands me a bit of paper with: "1.00, 0.376 and
> 0.904" on it, well that's just a list of values. However if if someone
> hands you a bit of paper with "Surface Gravity - Earth:1.00, Mars:
> 0.376 and Venus:0.904", or tells you those denotations, then we have
> data ;)

You have repeatedly chosen examples that suit your argument, whereas according to our disagreement only I that have that privilege!

Jim:

    In all examples, data is useful to the recipient and     represents facts

David:

  1. In all examples, data is useful to the recipient and represents values; and
  2. There exists example where data is useful to the recipient and doesn't represent facts

Since a tuple of a relation is a value and it also represents a fact it is clear that my definition of data encompasses yours.

We can both easily think of examples where (so called) data is useless to the recipient. Let's agree and say that's not actually data. That only leaves one possibility for proof by counter example: I provide an example where the data is useful to the recipient yet doesn't convey any facts. The sending of a poem or an image without any additional context is an example.

People download web pages (which are basically just encoded values) into their WWW browsers all the time without any more context than following a hyperlink. They often don't find out whether it's useful or relevant until they read it. In many respects the WWW can be regarded as a big collection of encoded "interesting values" indexed by content without any additional context. Received on Thu Feb 14 2008 - 04:52:38 CET

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