Metadata applications have developed local controlled vocabulary to meet information needs of users, but little is known about what vocabularies users use in searching for information. This paper reports the findings from an analysis of a digital library's query log. The analysis addresses questions of to what extent users use controlled vocabulary in resource discovery and what non-controlled vocabulary users use in their resource discovery. The authors discuss what is missing between the controlled and non-controlled vocabulary and how we can integrate user query terms into a learning object vocabulary for improving learning object representation and discovery.