> J has relational namespace layout:
> locales as tables and names as attributes.
I merely observed upon the structural features.
I cannot say right now about the exact mapping between
relational algebra and J operations. But I hope, J
operations are smaller building blocks, with which
the relational can be built.
--- Yuvaraj Athur Raghuvir <[EMAIL PROTECTED]> wrote:
> Oleg, maybe it is obvious to others but I am not able to understand
> what you want to state here.
>
> Would it be right to restate this as :
> -------------------------------------------------------------------------------------------
> One can think of relational algebra as applicable to the fundamental
> constructs of J language if one makes the following conceptual
> associations -
> Relational-Table <-> J Locale
> Relational-Table-Attributes <-> J Locale-Names
>
> {Since I have not followed much after that I assume you are proving
> the above statements using an example}
>
> So, by defining the operators of relational algebra, one can work
> across J Locales.
> -------------------------------------------------------------------------------------------
>
> Would this mean that a 'natural' mapping between Relational Constructs
> and J Constructs are as above?
> How will this mapping help?
> Or is it more an observation that brings together the fundamental
> concepts of Relational Algebra and J Constructs together?
>
> A little more on this would help. Thanks!
>
>
> On 10/24/06, Oleg Kobchenko <[EMAIL PROTECTED]> wrote:
> > J has relational namespace layout:
> > locales as tables and names as attributes.
> >
> >
> > NB. =========================================================
> >
> > require 'strings'
> >
> > cocurrent 'T1'
> >
> > B=: s: ','cut'one,two,three,four,five,six,seven,eight'
> > C=: 100+(#B)[EMAIL PROTECTED] 5
> > E=: 'ab'{~(#B) [EMAIL PROTECTED] 2
> >
> > cocurrent 'T2'
> >
> > D=: s: ','cut'uno,dos,tres,cuatro,cinco,seis,siete,ocho'
> > C=: 100+(#D)[EMAIL PROTECTED] 5
> > E=: 'ab'{~($D) [EMAIL PROTECTED] 2
> >
> > cocurrent 'base'
> >
> > jndx=: (0 , [EMAIL PROTECTED]) #: [: I.@, =/
> > sel=: ,.@:{
> >
> > 0 : 0
> > B_T1_ (,[EMAIL PROTECTED];]) C_T1_ ;&,. E_T1_
> > C_T2_ (,[EMAIL PROTECTED];]) D_T2_ ;&,. E_T2_
> >
> > ]'j1 j2'=. |:C_T1_ jndx C_T2_
> > (j1 sel B_T1_);(j1 sel C_T1_);(j2 sel D_T2_)
> >
> > ]'j1 j2'=. |:(C_T1_ jndx C_T2_) (e.#[) E_T1_ jndx E_T2_
> > (j1 sel B_T1_);(j1 sel C_T1_);(j1 sel E_T1_);(j2 sel D_T2_)
> > )
> >
> > NB. =========================================================
> >
> > B_T1_ (,[EMAIL PROTECTED];]) C_T1_ ;&,. E_T1_
> > +------+---+-+
> > |`one |101|a|
> > |`two |100|b|
> > |`three|104|b|
> > |`four |102|a|
> > |`five |104|a|
> > |`six |104|b|
> > |`seven|100|a|
> > |`eight|102|b|
> > +------+---+-+
> > C_T2_ (,[EMAIL PROTECTED];]) D_T2_ ;&,. E_T2_
> > +---+-------+-+
> > |101|`uno |a|
> > |100|`dos |b|
> > |104|`tres |b|
> > |102|`cuatro|a|
> > |104|`cinco |a|
> > |104|`seis |b|
> > |100|`siete |a|
> > |102|`ocho |b|
> > +---+-------+-+
> >
> > ]'j1 j2'=. |:C_T1_ jndx C_T2_
> > 0 1 1 2 2 2 3 3 4 4 4 5 5 5 6 6 7 7
> > 0 1 6 2 4 5 3 7 2 4 5 2 4 5 1 6 3 7
> > (j1 sel B_T1_);(j1 sel C_T1_);(j2 sel D_T2_)
> > +------+---+-------+
> > |`one |101|`uno |
> > |`two |100|`dos |
> > |`two |100|`siete |
> > |`three|104|`tres |
> > |`three|104|`cinco |
> > |`three|104|`seis |
> > |`four |102|`cuatro|
> > |`four |102|`ocho |
> > |`five |104|`tres |
> > |`five |104|`cinco |
> > |`five |104|`seis |
> > |`six |104|`tres |
> > |`six |104|`cinco |
> > |`six |104|`seis |
> > |`seven|100|`dos |
> > |`seven|100|`siete |
> > |`eight|102|`cuatro|
> > |`eight|102|`ocho |
> > +------+---+-------+
> >
> > ]'j1 j2'=. |:(C_T1_ jndx C_T2_) (e.#[) E_T1_ jndx E_T2_
> > 0 1 2 2 3 4 5 5 6 7
> > 0 1 2 5 3 4 2 5 6 7
> > (j1 sel B_T1_);(j1 sel C_T1_);(j1 sel E_T1_);(j2 sel D_T2_)
> > +------+---+-+-------+
> > |`one |101|a|`uno |
> > |`two |100|b|`dos |
> > |`three|104|b|`tres |
> > |`three|104|b|`seis |
> > |`four |102|a|`cuatro|
> > |`five |104|a|`cinco |
> > |`six |104|b|`tres |
> > |`six |104|b|`seis |
> > |`seven|100|a|`siete |
> > |`eight|102|b|`ocho |
> > +------+---+-+-------+
> >
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
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