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RE: How do you do 'table lookup' with n3?

From: Lund, Ben <B.Lund@nature.com>
Date: Wed, 8 Sep 2004 10:20:00 +0100
Message-ID: <125F7834E11A5741A7D79412EE3504F90B17ED61@UK1APPS2.nature.com>
To: "'Jones, David H'" <david.h.jones@boeing.com>
Cc: public-cwm-talk@w3.org

Hi David,

Jones, David H wrote:
> I'd like to be able to look up arbitrary values in a 
> table-like structure of rdf properties, but haven't been able 
> figure out how to do it using n3.  
> Can some one show an example of how to do this.  Below is my attempt.
> @prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
> @prefix owl:  <http://www.w3.org/2002/07/owl#> .
> @prefix log: <http://www.w3.org/2000/10/swap/log#>.
> @prefix math: <http://www.w3.org/2000/10/swap/math#>.
> @prefix string: <http://www.w3.org/2000/10/swap/string#>.
> # Lookup table
> [:letterGrade "A"; :numberGrade 10].
> [:letterGrade "B"; :numberGrade 7].
> [:letterGrade "C"; :numberGrade 5].
> [:letterGrade "D"; :numberGrade 3].
> [:letterGrade "F"; :numberGrade 1].
> :Dave :myLetterGrade "B".
> :Kathy :myLetterGrade "A".
> #Attempts at table lookup
> #{?y. ?x. :temp :val ?x.:numberGrade. ?y.:myLetterGrade 
> string:equalIgnoringCase ?x.:letterGrade } => {?y 
> :myNumberGrade :temp.:val}.
> {?y.:myLetterGrade string:equalIgnoringCase ?x.:letterGrade } 
> => {?y :myNumberGrade ?x.:numberGrade}.
> #Intended inferred properties
> #:Dave :myNumberGrade 5.
> #:Kathy :myNumberGrade 7.

You should explicitly name a variable for the node you want.  Changing your
rule to:
  ?y.:myLetterGrade string:equalIgnoringCase ?x.:letterGrade .
  ?x :numberGrade ?num . 
{ ?y :myNumberGrade ?num } .

gives you what you need.

$ cwm table.n3 results.n3  --filter=rules.n3
#Processed by Id: cwm.py,v 1.144 2003/09/14 20:20:20 timbl Exp
        #    using base file:/home/ben/devel/temp/

#  Notation3 generation by
#       notation3.py,v 1.146 2003/09/14 20:20:24 timbl Exp

#   Base was: file:/home/ben/devel/temp/
     @prefix : <results.n3#> .
     @prefix log: <http://www.w3.org/2000/10/swap/log#> .
     @prefix math: <http://www.w3.org/2000/10/swap/math#> .
     @prefix owl: <http://www.w3.org/2002/07/owl#> .
     @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
     @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
     @prefix string: <http://www.w3.org/2000/10/swap/string#> .
     @prefix table: <table.n3#> .

    :Dave     :myNumberGrade 7 .

    :Kathy     :myNumberGrade 10 .


(table.n3 contains the table, results.n3 contains the myLetterGrade
statements and rules.n3 contains the rule)



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Received on Wednesday, 8 September 2004 09:20:38 UTC

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