PREFIX  isa:  <http://purl.org/isaterms/>
PREFIX  obi:  <http://purl.obolibrary.org/obo/OBI_>
PREFIX  iao:  <http://purl.obolibrary.org/obo/IAO_>

SELECT DISTINCT ?study ?design_type ?design_type_label
WHERE
{
?study rdf:type isa:study.

#design_iri iao:denotes ?study.
?design_iri iao:0000219 ?study.

#?design_iri rdf:type obi:study_design
?design_iri rdf:type obi:0500000.

?design_iri rdf:type ?design_type.
OPTIONAL{
?design_type rdfs:label ?design_type_label.
}
}