Hi Mikael,
in the actual use case, we use a UNION inside the OPTIONAL:
SELECT ?employee ?reportsToEmployee ?reportsToEmployeeLabel WHERE {
GRAPH ?docGraph {
?doc sioc:has_container <https://localhost:4443/employees/>;
foaf:primaryTopic ?employee.
OPTIONAL { ?employee schema:sponsor ?reportsToEmployee. }
}
OPTIONAL {
{ ?reportsToEmployee <http://purl.org/dc/terms/title>
?reportsToEmployeeLabel. }
UNION
{ GRAPH ?reportsToEmployeeLabelGraph { ?reportsToEmployee
<http://purl.org/dc/terms/title> ?reportsToEmployeeLabel. } }
}
}
ORDER BY ?doc
which would not be equivalent to
SELECT ?employee ?reportsToEmployee ?reportsToEmployeeLabel WHERE {
GRAPH ?docGraph {
?doc sioc:has_container <https://localhost:4443/employees/>;
foaf:primaryTopic ?employee.
OPTIONAL { ?employee schema:sponsor ?reportsToEmployee. }
OPTIONAL {
{ ?reportsToEmployee <http://purl.org/dc/terms/title>
?reportsToEmployeeLabel. }
UNION
{ GRAPH ?reportsToEmployeeLabelGraph { ?reportsToEmployee
<http://purl.org/dc/terms/title> ?reportsToEmployeeLabel. } }
}
}
}
ORDER BY ?doc
And before using a workaround, I'd like to understand first which of
the implementations is correct.
On Tue, Nov 24, 2020 at 2:57 PM Mikael Pesonen
<[email protected]> wrote:
>
>
> Hi Martynas,
>
> I don't recall if nested graphs are allowed, but if so, this could work
> better
>
> SELECT ?employee ?reportsToEmployee ?reportsToEmployeeLabel WHERE {
> GRAPH ?docGraph {
> ?doc sioc:has_container<https://localhost:4443/employees/>;
> foaf:primaryTopic ?employee.
> OPTIONAL { ?employee schema:sponsor ?reportsToEmployee.
> OPTIONAL {
> GRAPH ?reportsToEmployeeLabelGraph { ?reportsToEmployee
> <http://purl.org/dc/terms/title> ?reportsToEmployeeLabel. }
> }
> }
> }
>
> }
> ORDER BY ?doc
>
>
> So second OPTIONAL inside the first one. That makes sure second OPTIONAL
> isn't left unbinded.
>
>
>
>
> On 24/11/2020 15.27, Martynas Jusevičius wrote:
> > Hi,
> >
> > despite using SPARQL for years, cases where different implementations
> > return different results leave me scratching my head. Can someone help
> > me out with this?
> >
> > I have a rather simple query:
> >
> > PREFIX schema: <https://schema.org/>
> > PREFIX foaf: <http://xmlns.com/foaf/0.1/>
> > PREFIX sioc: <http://rdfs.org/sioc/ns#>
> >
> > SELECT * WHERE {
> > GRAPH ?docGraph {
> > ?doc sioc:has_container <https://localhost:4443/employees/>;
> > foaf:primaryTopic ?employee.
> > OPTIONAL { ?employee schema:sponsor ?reportsToEmployee. }
> > }
> > }
> > ORDER BY ?doc
> >
> > Dydra returns 9 results:
> >
> > employee,reportsToEmployee
> > https://localhost:4443/employees/1/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/2/#this,
> > https://localhost:4443/employees/3/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/4/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/5/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/6/#this,https://localhost:4443/employees/5/#this
> > https://localhost:4443/employees/7/#this,https://localhost:4443/employees/5/#this
> > https://localhost:4443/employees/8/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/9/#this,https://localhost:4443/employees/5/#this
> >
> > Fuseki 3.16.0 returns 9 results:
> >
> > employee,reportsToEmployee
> > https://localhost:4443/employees/1/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/2/#this,
> > https://localhost:4443/employees/3/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/4/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/5/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/6/#this,https://localhost:4443/employees/5/#this
> > https://localhost:4443/employees/7/#this,https://localhost:4443/employees/5/#this
> > https://localhost:4443/employees/8/#this,https://localhost:4443/employees/2/#this
> > https://localhost:4443/employees/9/#this,https://localhost:4443/employees/5/#this
> >
> > So far so good -- the results are identical. Now I append an OPTIONAL
> > to the end of the query:
> >
> > PREFIX schema: <https://schema.org/>
> > PREFIX foaf: <http://xmlns.com/foaf/0.1/>
> > PREFIX sioc: <http://rdfs.org/sioc/ns#>
> >
> > SELECT ?employee ?reportsToEmployee ?reportsToEmployeeLabel WHERE {
> > GRAPH ?docGraph {
> > ?doc sioc:has_container <https://localhost:4443/employees/>;
> > foaf:primaryTopic ?employee.
> > OPTIONAL { ?employee schema:sponsor ?reportsToEmployee. }
> > }
> > OPTIONAL {
> > GRAPH ?reportsToEmployeeLabelGraph { ?reportsToEmployee
> > <http://purl.org/dc/terms/title> ?reportsToEmployeeLabel. }
> > }
> > }
> > ORDER BY ?doc
> >
> > Dydra returns 9 results:
> >
> > employee,reportsToEmployee,reportsToEmployeeLabel
> > https://localhost:4443/employees/1/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/2/#this,,
> > https://localhost:4443/employees/3/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/4/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/5/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/6/#this,https://localhost:4443/employees/5/#this,Buchanan
> > https://localhost:4443/employees/7/#this,https://localhost:4443/employees/5/#this,Buchanan
> > https://localhost:4443/employees/8/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/9/#this,https://localhost:4443/employees/5/#this,Buchanan
> >
> > Fuseki 3.16.0 returns 2400+ results:
> >
> > employee,reportsToEmployee,reportsToEmployeeLabel
> > https://localhost:4443/employees/1/#this,https://localhost:4443/employees/2/#this,Fuller
> > https://localhost:4443/employees/2/#this,https://localhost:4443/,Root
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/,Categories
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/1/,Beverages
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/1/#this,Beverages
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/2/,Condiments
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/2/#this,Condiments
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/3/,Confections
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/3/#this,Confections
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/4/,Dairy
> > Products
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/4/#this,Dairy
> > Products
> > https://localhost:4443/employees/2/#this,https://localhost:4443/categories/5/,Grains/Cereals
> > ....
> >
> > Dydra's result is the one I'm going after, and is based on my
> > understanding of OPTIONAL. But is it actually correct?
> >
> > And if Dydra is correct, what is Fuseki doing here? I would have
> > expected the ?reportsToEmployee bindings from the appended OPTIONAL to
> > be joined against the first result (without OPTIONAL), but that is not
> > the case?
> >
> > Thanks.
> >
> > Martynas
>
> --
> Lingsoft - 30 years of Leading Language Management
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> Mikael Pesonen
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>
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