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optional arcs implementation

From: Eric Prud'hommeaux <eric@w3.org>
Date: Fri, 11 Jun 2004 11:00:07 +0900
To: public-rdf-dawg@w3.org, Rob Shearer <Rob.Shearer@networkinference.com>
Message-ID: <20040611020007.GA12275@w3.org>

sorry for the delay in sending this out to you:

The algae code:

package W3C::Rdf::AlgaeCompileTree::Option;
sub evaluateQTerm {
    my ($self, $resultSet, $db, $modifier) = @_;

    for (my $e = $resultSet->elements; $e->hasMoreElements;) {
	my $row = $e->nextElement;
	my $miniResultSet = $row->makeResultSet;
	$self->{DECL}->evaluateQTerm($miniResultSet, $db, $modifier);
	my $empty = 1;
	for (my $miniE = $miniResultSet->elements; $miniE->hasMoreElements;) {
	    $empty = 0;
	    my $miniRow = $miniE->nextElement;
	    my $newRow = $row->duplicate;
	    $newRow->assumeNewBindings($miniRow);
	}
	if (!$empty) {
	    $row->eliminate;
	}
    }
}

The interface to the solution set is:
for each row
  for each new solution
    duplicate the row
    add the bindings to the new row
eliminate the original row

ala:
sub evaluateQTerm {
    for (my $e = $resultSet->elements; $e->hasMoreElements;) {
	my $row = $e->nextElement;
	for each solution
	    my $newRow = $row->duplicate;
	    $newRow->assumeNewBindings(solution);
	}
	$row->eliminate;
    }
}

Trivial test:
  ns <http://example.org/n#>
  assert (
   A p1 B .
   A p2 C .
   A p3 D .
  
   B p1 B .
   B p2 C )
  
  ask (
   ?n p1 B .
   ?n p2 C .
   ~?n p3 ?n2 )
  
  collect (?n ?n2)
got:
+------------------------+------------------------+
|                       n|                      n2|
|------------------------|------------------------|
|<http://example.org/n#B>|               !unbound!|
|<http://example.org/n#A>|<http://example.org/n#D>|
+------------------------+------------------------+

Testing for unintended extra resuts:
ns <http://example.org/n#>
  assert (
   A p1 B .
   A p2 C .
   A p3 D .
  
   D p4 E .
   E p5 F .
  
   D2 p4 E2 .
   E2 p5 F2 )
  
  ask (
   ?n p1 B .
   ?n p2 C .
   ~?n ?po ?n2 .
   ?n2 p4 ?n3 .
   ?n3 p5 ?n4)
  
  collect (?n ?n2 ?po)
got:
+------------------------+------------------------+-------------------------+
|                       n|                      n2|                       po|
|------------------------|------------------------|-------------------------|
|<http://example.org/n#A>|<http://example.org/n#D>|<http://example.org/n#p3>|
+------------------------+------------------------+-------------------------+

-- 
-eric

office: +1.617.258.5741 NE43-344, MIT, Cambridge, MA 02144 USA
cell:   +1.857.222.5741

(eric@w3.org)
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Received on Thursday, 10 June 2004 21:59:59 GMT

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