Problem with termtype guessing

[arenas-guerrero-julian]

Problem with termtype guessing

[chrdebru]

Yes. That's because rr:object "literal" is shorthand for rr:objectMap [ rr:constant "literal" ; ]. So in this case, there is sufficient information to deduce that the constant is a literal.

In short: rr:object is a shorthand for constant-based term maps.

[arenas-guerrero-julian]

Yes but imagine tou have rr:object "URI". What happens in that case?

[chrdebru]

You provide a literal. If you want to provide an IRI for a resource description, then you provide rr:object <http://example.org/foo> ;

• "http://foo/bar" is a literal
• "http://foo/bar"^^xsd:anyURI is a typed literal
• <http://foo/bar> is a named resource

[arenas-guerrero-julian]

I see then the R2RML spec is missing one point:

• It is a constant-based term map and the object is a literal.

[chrdebru]

The paragraph of the spec you are referring to is concerned with column-based term maps. rr:object (and rr:graph and rr:predicate, for that matter) are all shorthand for constant-based term maps.

[chrdebru]

The spec is clear in my opinion:

A constant-valued term map is a term map that ignores the logical table row and always generates the same RDF term. A constant-valued term map is represented by a resource that has exactly one rr:constant property.
The constant value of a constant-valued term map is the RDF term that is the value of its rr:constant property.
If the constant-valued term map is a subject map, predicate map or graph map, then its constant value must be an IRI.
If the constant-valued term map is an object map, then its constant value must be an IRI or literal.

When using rr:object, it is either an IRI or a literal, which is determined by "the syntax": <> vs. ""

[arenas-guerrero-julian]

Actually they have a note I did not see:

Constant-valued term maps are not considered as having a term type, and specifying rr:termType on these term maps has no effect. The type of the generated RDF term is determined directly by the value of rr:constant: If it is an IRI, then an IRI will be generated; if it is a literal, a literal will be generated.

Sorry, I think this can be closed :) thank you!