Separate but equal? a system comparison study of Medline's controlled vocabulary mesh

This study tests the effect of controlled vocabulary search feature implementation on retrieval rates in an online information systems environment. Four unique controlled vocabulary search features (Explode, Major Descriptor, Descriptor, Subheadings) were applied to nine search queries obtained from a medical reference librarian. The same queries were searched in the complete Medline file on the Dialog and Ovid systems. The unique records, i.e. those records retrieved in only one of the two systems, were identified and analyzed. Overall, the discrepancies in retrieval rates were not great and controlled vocabulary is shown to be an important and efficient way to search online information retrieval systems. However, Dialog did produce more records for each of the queries. The study also demonstrates that the user needs to be aware of system-specific designs which may prompt differing input strategies across different systems for the same unique controlled vocabulary search features.