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Bug #120

Repeated variables are not handled correctly

Added by Paula Gearon almost 16 years ago. Updated almost 16 years ago.

Status:
Closed
Priority:
Immediate
Assignee:
Paula Gearon
Category:
Mulgara
Target version:
SPARQL Query Engine
Start date:
Due date:
% Done:

0%

Estimated time:
Resolution:
fixed

Description

Basic graph patterns with repeated variables are not available in graphs defined with a variable.

Use the following mapping patterns (actual positions are variable):

($x $x * *) -> ($x $x1 * *) AND ($x1 $x * *)

($x $x $x *) -> ($x $x1 $x2 *) AND ($x2 $x $x1 *) AND ($x1 $x2 $x *)

($x $x $x $x) -> ($x $x1 $x2 $x3) AND ($x3 $x $x1 $x2) AND ($x2 $x3 $x $x1)

#1

Updated by Paula Gearon almost 16 years ago

  • Status changed from New to Closed
  • Resolution set to fixed

Turned out that this approach does NOT work, though it does come close. The reason why it doesn't work is apparent in the following data set:

  @prefix : <http://example.org/data/> .
  :y :y :x .
  :x :y :y .
  :y :x :y .

Instead, the transformation is now performed by changing the constraint to just one other form, but then wrapping it in a filter constraint set for SameTerm on the various forms of the repeated variable.

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