Multiple statements query SPARQL 1.1 property-paths Virtuoso 7.2.X

Question

A sample RDF dataset has entries owl#NamedIndividual grouped by owl#Class and a custom relation named IsMemberOf. When I try to obtain a list of results segregated by their type, it works well but the moment I add a way to obtain their corresponding IsMemberOf I don't get expected results.

Here is three SPARQL 1.1 queries I gave to Virtuoso (sample dataset below):

Query 1

sparql select * from 
where {
#If I uncomment the next line I don't get the proper results
#  ?s  ?member_of.
  ?s rdfs:label ?name.
  {
    ?s rdf:type/rdfs:subClassOf* .
  } UNION {
    ?s a .
  }
};

Query 2

sparql select * from 
where {
#If I uncomment the next line I get no results at all
#   ?s  ?member_of.
    ?s rdfs:label ?name.
    ?s rdf:type/rdfs:subClassOf* .
};

Query 3

sparql select * from 
where {
  ?s  ?member_of.
  ?s rdfs:label ?name.
  ?s rdf:type .
#If I replace the previous line with the next line I get no results at all
# ?s rdf:type/rdfs:subClassOf* .
};

This is how the data is grouped:

livingthings
->mammal
--->dog
----->doggy_the_dog
----->fido_the_dog
--->cat
---->katy_the_cat
--->elephant
----->eli_the_elephant
->reptile
--->snake
----->snakey_the_snake
nonlivingthings
->rock
--->rocky_the_rock
--->ralf_the_rock

group_a
->rocky_the_rock
->ralf_the_rock
->snakey_the_snake
->doggy_the_dog
group_b
->fido_the_dog
->katy_the_cat
group_c
->eli_the_elephant

Finaly here is the data I used

sparql create silent graph ;
sparql insert into graph  {
    .
    "Non-living things".
    .
    "Rock".
    .
    .
    .
    .
    "Rocky the rock".
    .
    .
    .
    "Ralf the rock".  
    .
    "Living things".
    .
    "Mammal".
    .
    .
    "Reptile".
    .
    .
    "Dog".
    .
    .
    "Cat".
    .
    .
    "Elephant".
    .
    .
    "Snake".
    .
    .
    .
    .
    "Snakey the snake".
    .
    .
    .
    "Doggy the dog".
    .
    .
    .
    "Fido the dog".
    .
    .
    .
    "Katy the cat".
    .
    .
    .
    "Eli the elephant".
};

Why do I only get the following incomplet result when I uncomment ?s ?member_of. in query one?

s               member_of   name
rocky_the_rock  group_a     Rocky the rock
ralf_the_rock   group_a     Ralf the rock

All of the results under the class are left out. Is it because of a bug in Virtuoso or the way my SPARQL query is formed?

Bob the mailman · Accepted Answer

Virtuoso seems to handle user defined relation oddly in a query when mixed with a property path.

Here is the Virtuoso specific way to address this issue.

Query 1 answer

sparql select * from 
where {
  ?s rdfs:label ?name.
  {
    ?s {1} ?member_of.
    ?s rdf:type/rdfs:subClassOf* .
  } UNION {
    ?s {1} ?member_of.
    ?s a .
  }
};

Query 2 answer

sparql select * from 
where {
    ?s {1} ?member_of.
    ?s rdfs:label ?name.
    ?s rdf:type/rdfs:subClassOf* .
};

Applying an explicit property path for the user defined relation as such ?s {1} ?member_of. gives the expected results.

In query one the line ?s {1} ?member_of. is applied to each term inside each union element. If not then the results are not as desired. It does solve the issue but it is a bit nonsensical. That is why I'll leave the question open for a few days to see if anyone can provide logical explanation to why things are that way in Virtuoso. If it's just a bug I'll contact them via their mailing list.

Multiple statements query SPARQL 1.1 property-paths Virtuoso 7.2.X

Answers (2)

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