Many-to-Many table in R2RML

Richard, all


This may be a dumb question, but I haven't been able to figure out how to
represent a many-to-many relationship in r2rml. For example:

Student(s_id, name)
Course(c_id, title)
Enrolled(s_id, c_id)

Where Enrolled is the many-to-many relationship.

These are the TripleMaps for the Student and Course table:

<#TriplesMap1>
    rr:logicalTable [ rr:tableName "student"; ]
    rr:subjectMap [
        rr:template "http://data.example.com/student/{s_id}";
        rr:class ex:Student;
    ];
    rr:predicateObjectMap [
        rr:predicateMap [ rr:predicate ex:name; ];
        rr:objectMap [ rr:column "name" ];
    ].

<#TriplesMap2>
    rr:logicalTable [ rr:tableName "course"; ]
    rr:subjectMap [
        rr:template "http://data.example.com/course/{c_id}";
        rr:class ex:Course;
    ];
    rr:predicateObjectMap [
        rr:predicateMap [ rr:predicate ex:title; ];
        rr:objectMap [ rr:column "title" ];
    ].

I assume that I should add a predicateObjectMap to TriplesMap1 (student)
which is going to connect to TriplesMap2 (course), but the joinCondition is
on the enrolled table.

<#TriplesMap1>
rr:predicateObjectMap [
        rr:predicateMap [ rr:predicate ex:isEnrolled; ];
        rr:objectMap [
            rr:parentTriplesMap <#TriplesMap2>;
            rr:joinCondition [
                rr:child "?????";
                rr:parent "???";
            ];
        ].

How is this suppose to be done? And could you add an example in the specs.

Thanks!

Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com