Re: [Virtuoso-users] Optional clause location in SPAQRL

[Rumi]

Hi Olga,


On 25-Jun-14 6:50 PM, Olga Medvedeva wrote:

Hi everyone,



1. Without any OPTIONAL numNames = 2143

PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT ?name) AS ?numNames
WHERE
{
   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
}

2. OPTIONAL at the beginning returns numNames = 1922

PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT ?name) AS ?numNames
WHERE
{
   OPTIONAL {?country dbpprop:yearEnd ?yearEnd}
   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
}



PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT ?name) AS ?numNames
WHERE
{
   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
   OPTIONAL {?country dbpprop:yearEnd ?yearEnd}
}



4. OPTIONAL at the end with not bound filter returns numNames = 338
PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT ?name) AS ?numNames
WHERE
{
   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
   OPTIONAL {?country dbpprop:yearEnd ?yearEnd} ## numNames = 2143
    FILTER (!bound(?yearEnd))
}

Does the location of OPTIONAL clause matters in SPAQRL query? Here are the examples of non-intersecting results on dbpedia: 3. OPTIONAL at the end returns numNames = 2143 - same as in #1 (without OPTIONAL) The difference is 221. And it's not equal to the number of not bounded ?yearEnd: I thought that the position of OPTIONAL clause in query should not affect the result. Why the results are so different?

In general yes, position for OPTIONAL should not matter.



-- integer: http://bit.ly/1lrGGHN
-- not integer: -- http://bit.ly/1lZ3L67
    -- ex. string: -- http://bit.ly/TAgOyl

I would suggest you to specify the type of the ?yearEnd ex.:

filter (  bif:isinteger (?yearEnd)) .


# demo link: -- http://bit.ly/1qe8eUf
PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT(?name))
WHERE
{

   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
   optional {?country dbpprop:yearEnd ?yearEnd }.
   filter (  bif:isinteger (?yearEnd)) .
}
limit 100

or

# demo link: -- http://bit.ly/UMdpgS
PREFIX dbprop: <http://dbpedia.org/property/>
SELECT count(DISTINCT(?name))
WHERE
{

   optional {?country dbpprop:yearEnd ?yearEnd }.
   ?country rdf:type dbpedia-owl:Country .
   ?country  dbprop:commonName ?name .
   filter (  bif:isinteger (?yearEnd)) .
}
limit 100





Best Regards,
Rumi Kocis

However, in your case ( let's say we run the queries against dbpedia.org/sparql endpoint ), there is data for ?yearEnd having different datatypes: integer, and non integer -- ex: both of which result in same total of 1839 and in both of which the position in OPTIONAL is different.

Thank you,
Olga Medvedeva.


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Open source business process management suite built on Java and Eclipse
Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
Winner of BOSSIE, CODIE, OW2 and Gartner awards
http://p.sf.net/sfu/Bonitasoft
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