Re: Multiple-Attribute Keys and 1NF
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Wed, 29 Aug 2007 21:42:51 -0300
Message-ID: <46d6123f$0$4056$9a566e8b_at_news.aliant.net>
>>"JOG" <j..._at_cs.nott.ac.uk> wrote in message
>>
>>news:1188393382.112445.286350_at_19g2000hsx.googlegroups.com...
>>
>>
>>
>>
>>>On Aug 29, 12:49 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>>
>>>>JOG wrote:
>>>>
>>>>>On Aug 29, 6:10 am, "David Cressey" <cresse..._at_verizon.net> wrote:
>>
>>>>>>"JOG" <j..._at_cs.nott.ac.uk> wrote in message
>>
>>>>>>news:1188327226.729673.127810_at_r34g2000hsd.googlegroups.com...
>>
>>>>>>>Okay, sure. But then to be able to query for green and yellow
>>>>>>>individually one must employ a further relation encoding two more
>>>>>>>propositions that state "'Green and yellow' contains 'Green'" and that
>>>>>>>"'Green and yellow' contains 'Yellow'" respectively. One then has a
>>>>>>>schema with two domains - one for the composites and one for
>>>>>>>individual colours (which is what I was inferring when I initially
>>>>>>>said a new one was being added).
>>
>>>>>>It took me a while to realize that what you meant from your original
>>>>>>description was that
>>>>>>"a green and yellow wire means earth". I had thought you meant "a
>>>>>>green
>>>>>>wire means earth" and "a yellow wire means earth". Pardon me for
>>>>>>being
>>>>>>dense.
>>
>>>>>>Clearly what we have here is not a domain of colors, but a domain of
>>>>>>color
>>>>>>codes, where a color code contains one or more colors, and maybe a
>>>>>>"thick
>>>>>>or thin" qualifier on each color.
>>
>>>>>>It's not clear to me why you need to able to query on simple colors,
>>>>>>unless
>>>>>>you need to decompose the color coding scheme into its constituent
>>>>>>parts for
>>>>>>some reason.
>>
>>>>>>There are lot of code domains where each code is made up of a set of
>>>>>>more
>>>>>>primitive elements.
>>>>>>Perhaps a very relevant one might be "character code". If I have the
>>>>>>following primitive elements:
>>
>>>>>>B1, B2, B4, B8, B16, B32, B64, B128
>>>>>>(which might be an odd way of labelling bits 0 through 7 of a byte), I
>>>>>>can
>>>>>>think of the character code for 'A' as being B64+B1. Now I could query
>>>>>>on
>>>>>>all the character codes without necessarily having an operator that
>>>>>>would
>>>>>>yield "all the codes that include B1".
>>
>>>>>>I think that the colors, as constituents of color codes, play the same
>>>>>>role
>>>>>>as bits, as constituents of character codes. Do you agree?
>>
>>>>>Yes. I mean no. No, yes. Gnngh ;)
>>
>>>>>Ok, of course I understand your point - a wire can be viewed as having
>>>>>a colour code, which itself has constituent parts. But its just one
>>>>>interpretation right. I am still seeing a difference between the
>>>>>propositions:
>>>>>* There is a colour-code "yellow and green" that denotes "earth".
>>>>>* The casing of an earth wire features the colour yellow and the
>>>>>colour green.
>>
>>>>>Its just like the difference between the propositions:
>>>>>* My office is B42
>>>>>* My office is on floor B, room 42.
>>
>>>>>There are instances where I may well want to encode as the second
>>>>>proposition forms. And /if/ that were the case (iff), well 1NF is
>>>>>precluding me from doing this in terms of the wire example.
>>
>>>>I disagree. You have already noted that 1NF allows this with exactly 2
>>>>relations (or with 1 relation and one or more operations on the color
>>>>code domain.)
>>
>>>True, I do see that, but it does so by requiring the invention of a
>>>colour-code concept which isn't in the proposition "The casing of an
>>>earth wire features the colour yellow and the colour green".
>>
>>You have to consider the entire relation value: what about the propositions
>>(treating or exclusively, of course):
>>
>>"The casing of a live wire features the colour brown or the colour red."
>>
>>"The casing of a neutral wire features the colour blue or the colour black."
>>
>>Write a predicate for the relation schema that when extentially quantified
>>and extended yields a set of atomic formulae that implies all three of the
>>propositions above. I think you'll find that the colour-code concept is in
>>that predicate.
Date: Wed, 29 Aug 2007 21:42:51 -0300
Message-ID: <46d6123f$0$4056$9a566e8b_at_news.aliant.net>
JOG wrote:
> On Aug 29, 7:03 pm, "Brian Selzer" <br..._at_selzer-software.com> wrote: >
>>"JOG" <j..._at_cs.nott.ac.uk> wrote in message
>>
>>news:1188393382.112445.286350_at_19g2000hsx.googlegroups.com...
>>
>>
>>
>>
>>>On Aug 29, 12:49 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>>
>>>>JOG wrote:
>>>>
>>>>>On Aug 29, 6:10 am, "David Cressey" <cresse..._at_verizon.net> wrote:
>>
>>>>>>"JOG" <j..._at_cs.nott.ac.uk> wrote in message
>>
>>>>>>news:1188327226.729673.127810_at_r34g2000hsd.googlegroups.com...
>>
>>>>>>>Okay, sure. But then to be able to query for green and yellow
>>>>>>>individually one must employ a further relation encoding two more
>>>>>>>propositions that state "'Green and yellow' contains 'Green'" and that
>>>>>>>"'Green and yellow' contains 'Yellow'" respectively. One then has a
>>>>>>>schema with two domains - one for the composites and one for
>>>>>>>individual colours (which is what I was inferring when I initially
>>>>>>>said a new one was being added).
>>
>>>>>>It took me a while to realize that what you meant from your original
>>>>>>description was that
>>>>>>"a green and yellow wire means earth". I had thought you meant "a
>>>>>>green
>>>>>>wire means earth" and "a yellow wire means earth". Pardon me for
>>>>>>being
>>>>>>dense.
>>
>>>>>>Clearly what we have here is not a domain of colors, but a domain of
>>>>>>color
>>>>>>codes, where a color code contains one or more colors, and maybe a
>>>>>>"thick
>>>>>>or thin" qualifier on each color.
>>
>>>>>>It's not clear to me why you need to able to query on simple colors,
>>>>>>unless
>>>>>>you need to decompose the color coding scheme into its constituent
>>>>>>parts for
>>>>>>some reason.
>>
>>>>>>There are lot of code domains where each code is made up of a set of
>>>>>>more
>>>>>>primitive elements.
>>>>>>Perhaps a very relevant one might be "character code". If I have the
>>>>>>following primitive elements:
>>
>>>>>>B1, B2, B4, B8, B16, B32, B64, B128
>>>>>>(which might be an odd way of labelling bits 0 through 7 of a byte), I
>>>>>>can
>>>>>>think of the character code for 'A' as being B64+B1. Now I could query
>>>>>>on
>>>>>>all the character codes without necessarily having an operator that
>>>>>>would
>>>>>>yield "all the codes that include B1".
>>
>>>>>>I think that the colors, as constituents of color codes, play the same
>>>>>>role
>>>>>>as bits, as constituents of character codes. Do you agree?
>>
>>>>>Yes. I mean no. No, yes. Gnngh ;)
>>
>>>>>Ok, of course I understand your point - a wire can be viewed as having
>>>>>a colour code, which itself has constituent parts. But its just one
>>>>>interpretation right. I am still seeing a difference between the
>>>>>propositions:
>>>>>* There is a colour-code "yellow and green" that denotes "earth".
>>>>>* The casing of an earth wire features the colour yellow and the
>>>>>colour green.
>>
>>>>>Its just like the difference between the propositions:
>>>>>* My office is B42
>>>>>* My office is on floor B, room 42.
>>
>>>>>There are instances where I may well want to encode as the second
>>>>>proposition forms. And /if/ that were the case (iff), well 1NF is
>>>>>precluding me from doing this in terms of the wire example.
>>
>>>>I disagree. You have already noted that 1NF allows this with exactly 2
>>>>relations (or with 1 relation and one or more operations on the color
>>>>code domain.)
>>
>>>True, I do see that, but it does so by requiring the invention of a
>>>colour-code concept which isn't in the proposition "The casing of an
>>>earth wire features the colour yellow and the colour green".
>>
>>You have to consider the entire relation value: what about the propositions
>>(treating or exclusively, of course):
>>
>>"The casing of a live wire features the colour brown or the colour red."
>>
>>"The casing of a neutral wire features the colour blue or the colour black."
>>
>>Write a predicate for the relation schema that when extentially quantified
>>and extended yields a set of atomic formulae that implies all three of the
>>propositions above. I think you'll find that the colour-code concept is in
>>that predicate.
> > I agree. I hold little stock with set based values so in RM I would go > for the addition of colour-code foreign key. > > But what if we weren't tied to a traditional relational schema and > tweaked the system so it could allow propositions with more than one > role of the same name without decomposing them. As Jan pointed out > 'tuples' are no longer functions - they would be unrestricted binary > relations (subsets of attribute x values). We could produce a > comparatively simpler and less cluttered schema, predicate in a very > similar manner as before, and with a few simple alterations could have > an equally effective WHERE mechanism. My concern however would be the > consequences to JOIN.
What would you offer in place of the RM's logical identity. Received on Thu Aug 30 2007 - 02:42:51 CEST