Yes, it looks like this is due to the different treatment of the named graphs.
PREFIX schema: <https://schema.org/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX sioc: <http://rdfs.org/sioc/ns#> SELECT (COUNT(?docGraph) AS ?docGraphCount) WHERE { GRAPH ?docGraph { ?doc sioc:has_container <https://localhost:4443/employees/>; foaf:primaryTopic ?employee. OPTIONAL { ?employee schema:sponsor ?reportsToEmployee. } } } Dydra: ?docGraphCount = 9 Fuseki: ?docGraphCount = 9 RDF4J: ?docGraphCount = 9 PREFIX schema: <https://schema.org/> PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX sioc: <http://rdfs.org/sioc/ns#> SELECT (COUNT(?reportsToEmployeeLabelGraph) AS ?reportsToEmployeeLabelGraphCount) WHERE { GRAPH ?reportsToEmployeeLabelGraph { ?reportsToEmployee <http://purl.org/dc/terms/title> ?reportsToEmployeeLabel. } } Dydra: ?reportsToEmployeeLabelGraphCount = 2409 Fuseki: ?reportsToEmployeeLabelGraphCount = 2409 RDF4J: ?reportsToEmployeeLabelGraphCount = 2409 On Tue, Nov 24, 2020 at 3:14 PM Lorenz Buehmann <buehm...@informatik.uni-leipzig.de> wrote: > > It looks more like the cartesian happens on the graphs - how many graph > do you have matching the first and the second part? > > On 24.11.20 14:27, 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
