+ <criteria> OPTIONAL {
+ ?work bf:workTitle ?wt .
+ ?wt bf:titleValue ?wtitle }
+ </criteria>
+ <criteria> OPTIONAL {
+ ?work bf:creator ?creator .
+ ?creator bf:label ?creatorlabel }
+ </criteria>
+ <criteria>OPTIONAL {
+ ?work bf:subject ?subject .
+ ?subject bf:label ?subjectlabel }
+ </criteria>