Fig. 1From: The Apollo Structured Vocabulary: an OWL2 ontology of phenomena in infectious disease epidemiology and population biology for use in epidemic simulationThe relationships of Apollo components and epidemic simulators. Apollo-SV defines the terminology used in Apollo XSD, which specifies the message syntax for the Web services. The SEUA calls the Broker service to configure simulators (messages passed along blue arrows) and to access simulator output (messages passed along red arrows). The Translator service translates Apollo messages to/from native simulator input/output. Purple ovals represent Apollo standards; blue ovals represent Apollo-developed software that use the Apollo Web services; and red ovals represent entities interacting with ApolloBack to article page