Re: Database design, Keys and some other things

I think it comes down to the fact, it is easy to confuse a predicate
with the situation it describes, but there is a real difference.
Consider the predicate:

"The sky is blue in the daytime"

This has may be represented a a set of three items {sky, blue,
daytime}. But we can say some extra things about this set. First who
stated it - me. Second when it was stated. Third that it is the first
thing I have said on the matter. Fourth, we can comment on the truth of
the statement - that it, in england, is only true.. say 25% of the
time. tops.

Now these are all pieces of information about the PREDICATE itself, not
the situation it describes. They are metadata, and encoding them with
the information about the situation is entirely incorrect - they are
attributes of the container, not of the content.

Mathematically we might write:

P = {"sky", "blue", "daytime"}
Author = {(P, "James")}
Created = {(P, "27th Sept 2005")}
etc...

Saying { sky, blue, daytime, James, "27th Sept 2005", 25% } is wholly
wrong. It is a confusion of data and meta data.

A surrogate key, created specifically to represent a statement, is no
different. It is an artificial way of referencing the predicate. This
is meta_data about the predicate and has no place existing in the same
area as the elements of the predicate - the real information, that
exists in the real world.

.

Relevant Pages

  • Re: Unreadable-object-p?
    ... to confuse everyone with this message: ... Does CL have a predicate for determining whether the printed ... (defun unreadable-object-p (obj) ...
    (comp.lang.lisp)
  • Re: Database design, Keys and some other things
    ... It is an artificial way of referencing the predicate. ... to me, as far as db or maybe i should say the RM rather than db as that is my interest, whether some value is metadata seems relative to the way it is used. ... i think this would mean that so as far as as the RM is concerned, the quote could equally mean "the daytime sky above James was 25% blue on Sept 27th" as well as lots of other things such as "James gets it right 25% of the time", or even "the sky *wasn't* blue, etc.". ...
    (comp.databases.theory)
  • Re: Database design, Keys and some other things
    ... > I think it comes down to the fact, it is easy to confuse a predicate ... > "The sky is blue in the daytime" ... > This has may be represented a a set of three items {sky, blue, ... That's a confusion allright, ...
    (comp.databases.theory)