Many fields have or are developing ontologies for their subdomains. The Gene Ontology (GO) is now considered to be a great success in biology, a field that has already developed several extensive ontologies. Similar advantages could accrue to the simulation and modeling community. Ontologies provide a way to establish common vocabularies and capture domain knowledge for organizing the domain with a community wide agreement or with the context of agreement between leading domain experts. They can be used to deliver significantly improved (semantic) search and browsing, integration of heterogeneous information sources, and improved analytics and knowledge discovery capabilities. Such knowledge can be used to establish common vocabularies, nomenclatures and taxonomies with links to detailed information sources. This paper investigates the use, the benefits and the development requirements of Web-accessible ontologies for discrete-event simulation and modeling. As a case study, the development of a prototype OWL-based ontology for modeling and simulation called the Discrete-event Modeling Ontology (DeMO) is also discussed. Prototype ontologies such as DeMO can serve as a basis for achieving broader community agreement and adoption of ontologies for this field.