comp.databases.theory Google Group

Re: teaching relational basics to people, questions

bbad...@pei.sympatico.ca (Bob Badour) — Tue, 12 Dec 2009 04:01:24 UT

1st normal form through 5th normal form involve lossless decomposition
by project. Fagin proved 5th normal form is necessary and sufficient to
avoid the update anomalies avoidable by lossless decomposition by project.
It has long been noted that one could create other normal forms using
different operations. e.g. lossless decomposition by restrict. However,

Re: teaching relational basics to people, questions

hidd...@gmail.com (Jan Hidders) — Mon, 12 Dec 2009 23:13:40 UT

Wikipedia is your friend:
<[link]>
Whether you can call it a normal form or not is of course largely a
matter of definition, but it clearly is different from the other ones.
It does for example not remove redundancy or update anomalies, which
was pretty much the whole point of the other normal forms.

Re: teaching relational basics to people, questions

r...@raampje.lan (Reinier Post) — Mon, 12 Dec 2009 22:07:31 UT

I don't think so. It's hard fo me to tell, because I just did the
required math and it turns out don't have $60 to spend on the book
which contains the definition of 6NF required for this discussion,
but if I can get by the Google Books preview, it appears to involve some
degree of interpretation of domain values (as being totally ordered).

Re: Fitch's paradox and OWA

r...@raampje.lan (Reinier Post) — Mon, 12 Dec 2009 21:41:46 UT

[...]
I just did.
Yes indeed, that's how they define K ... I should have seen that
the first time around. Thank you.
Now, the contradiction is direct: KP says that all
truths are knowable while NonO says that some truth isn't.
There is no paradox, just a contradiction.
But that's not how NonO is introduced:

Re: teaching relational basics to people, questions

vld...@yahoo.com (vldm10) — Mon, 12 Dec 2009 20:24:45 UT

I would appreciate it if you could give a definition of abstract and
concrete objects. Any definition, or rough description of abstract
objects can clarify these important things in your message which was
interesting.
As far as I know the following questions don’t have good answers:
What abstract objects are; how we know that they exist?

Re: teaching relational basics to people, questions

hidd...@gmail.com (Jan Hidders) — Fri, 12 Dec 2009 08:23:54 UT

Can I ask whether your question has been answered yet? I'm a bit
puzzled by it because this is basically a mathematical theorem and as
such the answer to it lies in understanding the math. But in your
additional text you seem to question more the philosophical /
intuitive foundations of these notions. Is that correct? And what is

Re: Fitch's paradox and OWA

do_not_re...@noone.com (Mr. Scott) — Fri, 12 Dec 2009 00:40:05 UT

Your addition of 'now' to (NonO) is the cause of your confusion. Go back
and re-read what you cited.
If K is the epistemic operator meaning 'it is known by someone at some time
that,' then not K would have to deny that, meaning 'it is not known by
anyone at any time that,' so with that in mind....

Re: Fitch's paradox and OWA

r...@raampje.lan (Reinier Post) — Thu, 12 Dec 2009 22:52:46 UT

I don't understand the paradox.
[link]
explains:
suppose that
(KP) all truths are knowable, i.e. can be known by somebody at some time
and
(NonO) not all truths are known now
then
(1) there is an unknown truth p
and then
(2) p is true and unknown is itself a truth

Re: Fitch's paradox and OWA

rea...@gmail.com (Nilone) — Thu, 12 Dec 2009 18:55:08 UT

Good point. I'm not sure that's what I want to say, either. I'll
give it some more thought.

Re: What would be a truly relational operating system ?

tkors...@gmail.com (Tonci Korsano) — Thu, 12 Dec 2009 16:10:57 UT

This is an interesting idea.
I don't know about making an os really relational.
However, it can still be a databased oriented or driven os.
For example, registry from windows, configuration files, and other os
files, could be xml.
I really mean a xml database oriented and driven operating system.
Xml files can store encrypted or ciphered data without problems (this

Call for Papers & Sessions: The 2010 International Conference on Software Engineering Research and Practice (SERP'10), USA, July 2010

amgs...@yahoo.com (A. M. G. Solo) — Thu, 12 Dec 2009 15:58:01 UT

It would be greatly appreciated if this announcement could be
shared with individuals whose research interests include
software engineering research and practice. Thanks.
-------
CALL FOR PAPERS
and
Call For Workshop/Session Proposals

Re: Fitch's paradox and OWA

hidd...@gmail.com (Jan Hidders) — Thu, 12 Dec 2009 14:51:36 UT

Which in my world view it is. It's positively weird to say that
Fermat's last theorem was not true until a proof was found. If you
want to do so, be my guest, but I'd argue you would be using another
definition of truth than I am.
-- Jan Hidders

Re: Fitch's paradox and OWA

rea...@gmail.com (Nilone) — Thu, 12 Dec 2009 09:22:09 UT

A relation with no attributes is a simple proposition, so you're
saying the chosen assumption is a value in the db, right? I prefer
this, although TTM states they subscribe to CWA.
Is it necessarily a db-wide choice, or could it be useful to
distinguish the choice per relation?

Re: Fitch's paradox and OWA

toledobythe...@oohay.ac (paul c) — Thu, 12 Dec 2009 03:06:42 UT

To be more clear/blunt, in the context of the RM, D&D have it that it is
a value of the relation that has no attributes. This may seem obscure
in general language, but in the db machine context it is much
simpler/clearer than the above.

Re: Fitch's paradox and OWA

rea...@gmail.com (Nilone) — Thu, 12 Dec 2009 02:56:14 UT

"All truths are known" is only problematic if you assume that truth
exists independent of cognition. From a phenomenalistic point of
view, both entities and predicates exist purely in the mind, which
means that all truths are known, but doesn't exclude the possibility
of creating new truths based on sense data. I'm currently leaning in