One of the main challenges in building enterprise applications has been to balance between built-in functionality and domain/scenario-specific customization. The lack of formal ways to extract, distill and standardize the embedded domain knowledge has been a barrier to effective and efficient customization. Ontology may provide, as many would hope, the much needed methodology and standard to achieve the objective of building flexible enterprise solutions. This article examines the uses, issues and challenges of using ontology in enterprise applications. We believe that we are seriously lacking in modeling methodology, domain user tools, and lifecycle management methodology for the creation and maintenance of ontology on a large deployable scale. We present the issues based on an ongoing project to build a product ontology for a public procurement system. Through real life scenarios, we are hoping to convey important research directions to better enable ontology.