This document discusses the maturity of ontology development as an engineering discipline. It analyzes ontology development using the Capability Maturity Model (CMM), which assesses the formality and optimization of software development processes. While ontology development has established technologies and methods, it still relies heavily on ad hoc practices. The document argues ontology development would benefit from increased understanding of development processes, tool support for those processes, and the ability to quantitatively measure and manage processes. This would help move ontology development from a reliance on individual expertise to more mature and repeatable engineering practices.