At a quick glance, it appears that the OPAC determines whether a title has holdable copies by looking at //*[local-name()="holdings" and @has_holdable="true"] in the unAPI representation of the record. So that might be the place to look.
At a quick glance, it appears that the OPAC determines whether a title has holdable copies by looking at //*[local- name()= "holdings" and @has_holdable= "true"] in the unAPI representation of the record. So that might be the place to look.