The Ontology for Biomedical Investigations (OBI), written in OWL DL, is being developed by a large consortium seeking to provide a crossdomain, shared framework for representing investigations in the biological and biomedical sciences. In this paper we report our experiences and describe our development process as it pertains to OWL, which includes a number of elements that might inform tool developers as well as suggest general development patterns. Finally, we review where improvements to OWL and OWL related tools might be beneficial.