Date: Feb 9, 2013 1:14 AM
Author: Graham Cooper
Subject: Re: >>>BLoCK PROLOG 1st QUERY<<<

On Feb 9, 1:18 pm, Graham Cooper <grahamcoop...@gmail.com> wrote:
> QUERY:  f [a [b d]] ?
>
>
>
> > TABLE QUERY
> > ref     term    buds
> > 1       f       0
> > 21      a       0
> > 221     b       0       <-------
> > 222     d       0       <-------
> > 1       *       0
> > 21      *       0
> > 2       *       2
> > 221     *       0
> > 22      *       1         <--------
> > 222     *       0
>
> Simple explanation!
>
> If b and d don't get matched
> you can still match Position 22 to a VAR instead
> and subtract 1 from the expected matched terms!
>


In this example:

f  [ a  [ b d ]] ?       4 TERM QUERY

|      |     |

f     a   D                2 TERM + 1 VAR  =  3 MATCHING ROWS


so this SQL clause finds all Predicates with matching terms (all in
the right position)

QUERY.ref=HEADS.ref AND QUERY.term=HEADS.term
GROUP BY HID HAVING COUNT(HID)=$qc-SUM(QB)";


and COUNT(HEAD.ID) = 3
QC = Query Term Count = 4

SUM(BUDS) = 1

So 4-1 = 3 records found!

So it should return this Predicate in the Results.

QUERY:   f [a [b d]]      4 - 1 bud
RESULT:  f a D            3

EASY!

All that's left is Variable Binding and Tail Recursion..

Herc
--
www.BLoCKPROLOG.com