Knowledge Graphs

Exercise 2.3 - SPARQL Queries

The following SPARQL query illustrates the use of OPTIONAL graph patterns. Within each result returned by this query, what is the minimum and the maximum possible data items it must much:

SELECT ?foafName ?mbox ?gname ?fname
WHERE
{ ?x foaf:name ?foafName .
    OPTIONAL { ?x foaf:mbox ?mbox } .
    OPTIONAL { ?x vcard:N ?vc .
        ?vc vcard:Given ?gname .
        OPTIONAL { ?vc vcard:Family ?fname }
              }
}
(a) minimum 4 / maximum 4
(b) minimum 0 / maximum 4
(c) minimum 1 / maximum 4
(d) minimum 2 / maximum 4
(e) minimum 1 / maximum 3