Different query results when using named graphs

[Amin Tajgardoon]

Hi,

Based on this post on Stackoverflow I am trying to get depth of sub-classes in the class hierarchy, with the following query:

SELECT DISTINCT ?topLevel ?subClass ?directParent  (count(?mid) as ?depth)

FROM <tag:stardog:api:context:all>

WHERE{

  #get the top level classes

  ?topLevel rdf:type owl:Class .

 

  #get ?subClasses of ?topLevel classes

  ?mid rdfs:subClassOf* ?topLevel .

  ?subClass rdfs:subClassOf+ ?mid .

 

  #get the ?directParent of each subClass

  ?subClass rdfs:subClassOf ?directParent .

 

    }

GROUP BY ?topLevel ?subClass ?directParent

ORDER BY ?topLevel  ?depth

Although it completely works when all owl files are loaded  into the default graph, when I use 2 named graphs to split my classes, the same query returns wrong depths for sub-classes. Everything else in the results looks the same.

I tried Stardog 2.2.1 and 2.1.3.

I am wondering why the behavior is different when I use named graphs!

Please help me, I really need to split the data among separate named graphs.

Thanks you.

[Mike Grove]

For what it's worth, the spec forbids [1] what you're trying to do: "A property path does not span multiple graphs in a dataset."

If you want to provide the data to go with your query, and how it's partitioned into named graphs, we can take a look.  Our implementation doesn't strictly follow 18.1.7, so in theory, it may work.  But you should know that what you're doing it's very portable.

Cheers,

Mike

[1] http://www.w3.org/TR/sparql11-query/#sparqlPropertyPaths

 

Please help me, I really need to split the data among separate named graphs.

Thanks you.

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[Amin Tajgardoon]

Alright. I created the same tree in the stackoverflow post as two separate files, each containing a portion of the tree, using rdfs:subClassOf relationship. I ran the following query which is basically the same as in my last post, against two instances of Stardog 2.1.3 database; in one I loaded both owl files in the default context, in the other one, files were loaded into two separate named graphs (contexts). Here is how I did it via CLI:

>stardog data add --named-graph http://www.example.org/schema1 -- MYDB Desktop\Tree1.owl

>stardog data add --named-graph http://www.example.org/schema2 -- MYDB Desktop\Tree2.owl

Here is the query:

SELECT DISTINCT ?superLabel ?subLabel (count(?mid) as ?d)

FROM<tag:stardog:api:context:all>

WHERE{

  ?mid rdfs:subClassOf* ?super .

  ?sub   rdfs:subClassOf+ ?mid  .

  ?super rdfs:label ?superLabel .

  ?sub rdfs:label ?subLabel .

} 

GROUP BY ?superLabel ?subLabel 

ORDER BY ?superLabel ?d

Here is the Result:

+------------+----------+-------+

| superLabel | subLabel |   d   |

+------------+----------+-------+

| "A"        | "B"      | 1     |

| "A"        | "C"      | 1     |

| "A"        | "D"      | 1     |

| "A"        | "E"      | 2     |

| "A"        | "F"      | 2     |

| "A"        | "G"      | 3     |

| "A"        | "H"      | 4     |

| "B"        | "F"      | 1     |

| "B"        | "E"      | 1     |

| "B"        | "G"      | 2     |

| "B"        | "H"      | 3     |

| "E"        | "G"      | 2     |

| "E"        | "H"      | 3     |

| "G"        | "H"      | 1     |

+------------+----------+-------+

Wrong results are highlighted above. Note that G and H are in schema2 context and others are in schema1.

I've attached the 2 files which I created in Protege.

Thank you for helping me.

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Amin

[Amin Tajgardoon]

Has anybody looked at my problem by any chance?

--

Amin